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	$70.72	11.475%	$78.8351	$78.84	$78.85	$78.80
Purchase #2	$41.32	9.295%	$45.1607	$45.16	$45.15	$45.20
Purchase #3	$119.39	8.629%	$129.6922	$129.69	$129.70	$129.70
Purchase #4	$162.81	11.807%	$182.033	$182.03	$182.05	$182.00
Purchase #5	$158.38	4.795%	$165.9743	$165.97	$165.95	$166.00
Purchase #6	$39.55	4.780%	$41.4405	$41.44	$41.45	$41.40
Purchase #7	$231.51	11.180%	$257.3928	$257.39	$257.40	$257.40
7 purchase totals =	$823.68		$900.5286	$900.52	$900.55	$900.50