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	$86.66	4.508%	$90.5666	$90.57	$90.55	$90.60
Purchase #2	$51.66	7.255%	$55.4079	$55.41	$55.40	$55.40
Purchase #3	$248.86	6.407%	$264.8045	$264.80	$264.80	$264.80
Purchase #4	$188.29	13.608%	$213.9125	$213.91	$213.90	$213.90
Purchase #5	$154.62	8.831%	$168.2745	$168.27	$168.25	$168.30
Purchase #6	$224.55	9.753%	$246.4504	$246.45	$246.45	$246.50
Purchase #7	$6.58	6.175%	$6.9863	$6.99	$7.00	$7.00
7 purchase totals =	$961.22		$1,046.4027	$1,046.40	$1,046.35	$1,046.50