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	$14.41	11.792%	$16.1092	$16.11	$16.10	$16.10
Purchase #2	$25.72	5.559%	$27.1498	$27.15	$27.15	$27.10
Purchase #3	$200.54	4.268%	$209.099	$209.10	$209.10	$209.10
Purchase #4	$132.55	13.846%	$150.9029	$150.90	$150.90	$150.90
Purchase #5	$229.61	10.685%	$254.1438	$254.14	$254.15	$254.10
Purchase #6	$147.28	8.455%	$159.7325	$159.73	$159.75	$159.70
Purchase #7	$238.37	12.204%	$267.4607	$267.46	$267.45	$267.50
7 purchase totals =	$988.48		$1,084.5979	$1,084.59	$1,084.60	$1,084.50