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	$241.47	5.732%	$255.3111	$255.31	$255.30	$255.30
Purchase #2	$55.67	5.339%	$58.6422	$58.64	$58.65	$58.60
Purchase #3	$168.56	10.632%	$186.4813	$186.48	$186.50	$186.50
Purchase #4	$229.64	12.199%	$257.6538	$257.65	$257.65	$257.70
Purchase #5	$10.70	7.648%	$11.5183	$11.52	$11.50	$11.50
Purchase #6	$194.44	9.290%	$212.5035	$212.50	$212.50	$212.50
Purchase #7	$66.54	7.228%	$71.3495	$71.35	$71.35	$71.30
7 purchase totals =	$967.02		$1,053.4597	$1,053.45	$1,053.45	$1,053.40