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	$227.67	8.471%	$246.9559	$246.96	$246.95	$247.00
Purchase #2	$83.64	6.680%	$89.2272	$89.23	$89.25	$89.20
Purchase #3	$172.58	4.823%	$180.9035	$180.90	$180.90	$180.90
Purchase #4	$249.33	5.275%	$262.4822	$262.48	$262.50	$262.50
Purchase #5	$142.47	4.364%	$148.6874	$148.69	$148.70	$148.70
Purchase #6	$234.33	9.382%	$256.3148	$256.31	$256.30	$256.30
Purchase #7	$85.41	4.356%	$89.1305	$89.13	$89.15	$89.10
7 purchase totals =	$1,195.43		$1,273.7015	$1,273.70	$1,273.75	$1,273.70