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	$204.97	8.340%	$222.0645	$222.06	$222.05	$222.10
Purchase #2	$170.97	5.604%	$180.5512	$180.55	$180.55	$180.60
Purchase #3	$53.47	11.266%	$59.4939	$59.49	$59.50	$59.50
Purchase #4	$37.53	12.293%	$42.1436	$42.14	$42.15	$42.10
Purchase #5	$245.74	12.623%	$276.7598	$276.76	$276.75	$276.80
Purchase #6	$249.74	9.140%	$272.5662	$272.57	$272.55	$272.60
Purchase #7	$235.47	10.194%	$259.4738	$259.47	$259.45	$259.50
7 purchase totals =	$1,197.89		$1,313.0530	$1,313.04	$1,313.00	$1,313.20