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	$54.56	12.654%	$61.464	$61.46	$61.45	$61.50
Purchase #2	$39.47	6.663%	$42.0999	$42.10	$42.10	$42.10
Purchase #3	$233.28	10.364%	$257.4571	$257.46	$257.45	$257.50
Purchase #4	$51.29	11.644%	$57.2622	$57.26	$57.25	$57.30
Purchase #5	$155.90	5.820%	$164.9734	$164.97	$164.95	$165.00
Purchase #6	$65.77	8.692%	$71.4867	$71.49	$71.50	$71.50
Purchase #7	$209.34	10.515%	$231.3521	$231.35	$231.35	$231.40
7 purchase totals =	$809.61		$886.0954	$886.09	$886.05	$886.30