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	$105.56	5.753%	$111.6329	$111.63	$111.65	$111.60
Purchase #2	$76.96	5.120%	$80.9004	$80.90	$80.90	$80.90
Purchase #3	$51.71	13.333%	$58.6045	$58.60	$58.60	$58.60
Purchase #4	$59.59	3.746%	$61.8222	$61.82	$61.80	$61.80
Purchase #5	$243.83	3.811%	$253.1224	$253.12	$253.10	$253.10
Purchase #6	$243.85	6.598%	$259.9392	$259.94	$259.95	$259.90
Purchase #7	$28.41	7.447%	$30.5257	$30.53	$30.55	$30.50
7 purchase totals =	$809.91		$856.5473	$856.54	$856.55	$856.40