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	$108.93	12.625%	$122.6824	$122.68	$122.70	$122.70
Purchase #2	$40.29	11.798%	$45.0434	$45.04	$45.05	$45.00
Purchase #3	$99.29	12.135%	$111.3388	$111.34	$111.35	$111.30
Purchase #4	$63.73	11.598%	$71.1214	$71.12	$71.10	$71.10
Purchase #5	$65.63	4.385%	$68.5079	$68.51	$68.50	$68.50
Purchase #6	$155.76	4.171%	$162.2567	$162.26	$162.25	$162.30
Purchase #7	$73.79	11.521%	$82.2913	$82.29	$82.30	$82.30
7 purchase totals =	$607.42		$663.2419	$663.24	$663.25	$663.20