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	$93.80	7.200%	$100.5536	$100.55	$100.55	$100.60
Purchase #2	$199.65	9.743%	$219.1019	$219.10	$219.10	$219.10
Purchase #3	$138.60	9.776%	$152.1495	$152.15	$152.15	$152.10
Purchase #4	$56.66	5.107%	$59.5536	$59.55	$59.55	$59.60
Purchase #5	$179.61	9.507%	$196.6855	$196.69	$196.70	$196.70
Purchase #6	$170.25	8.284%	$184.3535	$184.35	$184.35	$184.40
Purchase #7	$148.28	11.643%	$165.5442	$165.54	$165.55	$165.50
7 purchase totals =	$986.85		$1,077.9418	$1,077.93	$1,077.95	$1,078.00