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	$183.29	10.375%	$202.3063	$202.31	$202.30	$202.30
Purchase #2	$185.33	8.277%	$200.6698	$200.67	$200.65	$200.70
Purchase #3	$55.61	6.113%	$59.0094	$59.01	$59.00	$59.00
Purchase #4	$101.64	9.216%	$111.0071	$111.01	$111.00	$111.00
Purchase #5	$58.61	4.418%	$61.1994	$61.20	$61.20	$61.20
Purchase #6	$117.56	7.162%	$125.9796	$125.98	$126.00	$126.00
Purchase #7	$174.48	9.742%	$191.4778	$191.48	$191.50	$191.50
7 purchase totals =	$876.52		$951.6494	$951.66	$951.65	$951.70