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	$235.33	7.737%	$253.5375	$253.54	$253.55	$253.50
Purchase #2	$102.26	9.224%	$111.6925	$111.69	$111.70	$111.70
Purchase #3	$233.32	8.742%	$253.7168	$253.72	$253.70	$253.70
Purchase #4	$104.55	6.707%	$111.5622	$111.56	$111.55	$111.60
Purchase #5	$180.75	7.625%	$194.5322	$194.53	$194.55	$194.50
Purchase #6	$192.73	13.831%	$219.3865	$219.39	$219.40	$219.40
Purchase #7	$140.67	10.327%	$155.197	$155.20	$155.20	$155.20
7 purchase totals =	$1,189.61		$1,299.6247	$1,299.63	$1,299.65	$1,299.60