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	$41.68	9.292%	$45.5529	$45.55	$45.55	$45.60
Purchase #2	$165.75	9.408%	$181.3438	$181.34	$181.35	$181.30
Purchase #3	$198.78	10.180%	$219.0158	$219.02	$219.00	$219.00
Purchase #4	$228.92	12.725%	$258.0501	$258.05	$258.05	$258.10
Purchase #5	$33.72	7.613%	$36.2871	$36.29	$36.30	$36.30
Purchase #6	$59.37	13.534%	$67.4051	$67.41	$67.40	$67.40
Purchase #7	$242.47	13.473%	$275.138	$275.14	$275.15	$275.10
7 purchase totals =	$970.69		$1,082.7928	$1,082.80	$1,082.80	$1,082.80