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	$111.95	13.822%	$127.4237	$127.42	$127.40	$127.40
Purchase #2	$57.93	4.405%	$60.4818	$60.48	$60.50	$60.50
Purchase #3	$203.89	11.364%	$227.0601	$227.06	$227.05	$227.10
Purchase #4	$148.35	3.437%	$153.4488	$153.45	$153.45	$153.40
Purchase #5	$185.30	10.351%	$204.4804	$204.48	$204.50	$204.50
Purchase #6	$236.45	4.734%	$247.6435	$247.64	$247.65	$247.60
Purchase #7	$135.43	6.273%	$143.9255	$143.93	$143.95	$143.90
7 purchase totals =	$1,079.30		$1,164.4638	$1,164.46	$1,164.50	$1,164.40