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	$118.70	10.168%	$130.7694	$130.77	$130.75	$130.80
Purchase #2	$185.60	7.399%	$199.3325	$199.33	$199.35	$199.30
Purchase #3	$70.89	12.694%	$79.8888	$79.89	$79.90	$79.90
Purchase #4	$78.49	12.848%	$88.5744	$88.57	$88.55	$88.60
Purchase #5	$201.69	12.291%	$226.4797	$226.48	$226.50	$226.50
Purchase #6	$162.91	13.796%	$185.3851	$185.39	$185.40	$185.40
Purchase #7	$141.90	6.651%	$151.3378	$151.34	$151.35	$151.30
7 purchase totals =	$960.18		$1,061.7677	$1,061.77	$1,061.80	$1,061.80