Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.77	5.607%	$157.1115	$157.11	$157.10	$157.10
Purchase #2	$232.42	12.842%	$262.2674	$262.27	$262.25	$262.30
Purchase #3	$91.31	12.771%	$102.9712	$102.97	$102.95	$103.00
Purchase #4	$160.80	4.547%	$168.1116	$168.11	$168.10	$168.10
Purchase #5	$182.83	4.151%	$190.4193	$190.42	$190.40	$190.40
Purchase #6	$104.26	11.772%	$116.5335	$116.53	$116.55	$116.50
Purchase #7	$93.91	9.685%	$103.0052	$103.01	$103.00	$103.00
7 purchase totals =	$1,014.30		$1,100.4197	$1,100.42	$1,100.35	$1,100.40