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	$32.27	7.598%	$34.7219	$34.72	$34.70	$34.70
Purchase #2	$196.56	7.784%	$211.8602	$211.86	$211.85	$211.90
Purchase #3	$163.46	9.453%	$178.9119	$178.91	$178.90	$178.90
Purchase #4	$85.96	13.365%	$97.4486	$97.45	$97.45	$97.40
Purchase #5	$55.84	11.426%	$62.2203	$62.22	$62.20	$62.20
Purchase #6	$77.77	7.573%	$83.6595	$83.66	$83.65	$83.70
Purchase #7	$64.51	10.494%	$71.2797	$71.28	$71.30	$71.30
7 purchase totals =	$676.37		$740.1021	$740.10	$740.05	$740.10