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	$168.33	13.581%	$191.1909	$191.19	$191.20	$191.20
Purchase #2	$116.56	9.225%	$127.3127	$127.31	$127.30	$127.30
Purchase #3	$10.51	8.118%	$11.3632	$11.36	$11.35	$11.40
Purchase #4	$76.60	12.638%	$86.2807	$86.28	$86.30	$86.30
Purchase #5	$221.75	4.344%	$231.3828	$231.38	$231.40	$231.40
Purchase #6	$52.40	5.606%	$55.3375	$55.34	$55.35	$55.30
Purchase #7	$249.43	9.227%	$272.4449	$272.44	$272.45	$272.40
7 purchase totals =	$895.58		$975.3127	$975.30	$975.35	$975.30