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	$109.95	7.451%	$118.1424	$118.14	$118.15	$118.10
Purchase #2	$159.41	13.478%	$180.8953	$180.90	$180.90	$180.90
Purchase #3	$116.89	5.853%	$123.7316	$123.73	$123.75	$123.70
Purchase #4	$62.29	8.538%	$67.6083	$67.61	$67.60	$67.60
Purchase #5	$80.40	10.363%	$88.7319	$88.73	$88.75	$88.70
Purchase #6	$31.58	3.556%	$32.703	$32.70	$32.70	$32.70
Purchase #7	$170.46	5.869%	$180.4643	$180.46	$180.45	$180.50
7 purchase totals =	$730.98		$792.2768	$792.27	$792.30	$792.20