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	$183.34	11.131%	$203.7476	$203.75	$203.75	$203.70
Purchase #2	$224.97	9.782%	$246.9766	$246.98	$247.00	$247.00
Purchase #3	$50.42	9.421%	$55.1701	$55.17	$55.15	$55.20
Purchase #4	$33.43	11.339%	$37.2206	$37.22	$37.20	$37.20
Purchase #5	$96.31	4.349%	$100.4985	$100.50	$100.50	$100.50
Purchase #6	$155.45	10.300%	$171.4614	$171.46	$171.45	$171.50
Purchase #7	$89.72	11.126%	$99.7022	$99.70	$99.70	$99.70
7 purchase totals =	$833.64		$914.7770	$914.78	$914.75	$914.80