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	$214.61	3.531%	$222.1879	$222.19	$222.20	$222.20
Purchase #2	$55.63	11.562%	$62.0619	$62.06	$62.05	$62.10
Purchase #3	$243.66	13.815%	$277.3216	$277.32	$277.30	$277.30
Purchase #4	$91.53	8.211%	$99.0455	$99.05	$99.05	$99.00
Purchase #5	$100.69	11.184%	$111.9512	$111.95	$111.95	$112.00
Purchase #6	$233.64	12.533%	$262.9221	$262.92	$262.90	$262.90
Purchase #7	$212.67	7.353%	$228.3076	$228.31	$228.30	$228.30
7 purchase totals =	$1,152.43		$1,263.7978	$1,263.80	$1,263.75	$1,263.80