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	$154.37	3.490%	$159.7575	$159.76	$159.75	$159.80
Purchase #2	$212.89	3.114%	$219.5194	$219.52	$219.50	$219.50
Purchase #3	$196.98	10.144%	$216.9617	$216.96	$216.95	$217.00
Purchase #4	$131.32	9.191%	$143.3896	$143.39	$143.40	$143.40
Purchase #5	$104.96	6.463%	$111.7436	$111.74	$111.75	$111.70
Purchase #6	$159.70	3.645%	$165.5211	$165.52	$165.50	$165.50
Purchase #7	$232.32	6.541%	$247.5161	$247.52	$247.50	$247.50
7 purchase totals =	$1,192.54		$1,264.4090	$1,264.41	$1,264.35	$1,264.40