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	$117.34	10.167%	$129.27	$129.27	$129.25	$129.30
Purchase #2	$236.98	12.111%	$265.6806	$265.68	$265.70	$265.70
Purchase #3	$40.27	12.852%	$45.4455	$45.45	$45.45	$45.40
Purchase #4	$88.88	13.754%	$101.1046	$101.10	$101.10	$101.10
Purchase #5	$67.31	6.657%	$71.7908	$71.79	$71.80	$71.80
Purchase #6	$47.46	10.149%	$52.2767	$52.28	$52.30	$52.30
Purchase #7	$55.62	10.456%	$61.4356	$61.44	$61.45	$61.40
7 purchase totals =	$653.86		$727.0038	$727.01	$727.05	$727.00