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	$17.61	3.146%	$18.164	$18.16	$18.15	$18.20
Purchase #2	$31.43	4.731%	$32.917	$32.92	$32.90	$32.90
Purchase #3	$35.83	12.395%	$40.2711	$40.27	$40.25	$40.30
Purchase #4	$106.81	13.389%	$121.1108	$121.11	$121.10	$121.10
Purchase #5	$232.82	13.714%	$264.7489	$264.75	$264.75	$264.70
Purchase #6	$218.90	5.587%	$231.1299	$231.13	$231.15	$231.10
Purchase #7	$50.25	6.191%	$53.361	$53.36	$53.35	$53.40
7 purchase totals =	$693.65		$761.7027	$761.70	$761.65	$761.70