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	$188.38	10.623%	$208.3916	$208.39	$208.40	$208.40
Purchase #2	$151.76	13.692%	$172.539	$172.54	$172.55	$172.50
Purchase #3	$210.48	7.306%	$225.8577	$225.86	$225.85	$225.90
Purchase #4	$82.91	4.742%	$86.8416	$86.84	$86.85	$86.80
Purchase #5	$71.61	6.302%	$76.1229	$76.12	$76.10	$76.10
Purchase #6	$209.75	7.732%	$225.9679	$225.97	$225.95	$226.00
Purchase #7	$93.94	11.811%	$105.0353	$105.04	$105.05	$105.00
7 purchase totals =	$1,008.83		$1,100.7560	$1,100.76	$1,100.75	$1,100.70