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	$249.48	5.816%	$263.9898	$263.99	$264.00	$264.00
Purchase #2	$9.57	13.769%	$10.8877	$10.89	$10.90	$10.90
Purchase #3	$175.48	11.825%	$196.2305	$196.23	$196.25	$196.20
Purchase #4	$129.61	9.472%	$141.8867	$141.89	$141.90	$141.90
Purchase #5	$218.61	13.299%	$247.6829	$247.68	$247.70	$247.70
Purchase #6	$19.45	5.507%	$20.5211	$20.52	$20.50	$20.50
Purchase #7	$188.97	7.650%	$203.4262	$203.43	$203.45	$203.40
7 purchase totals =	$991.17		$1,084.6249	$1,084.63	$1,084.70	$1,084.60