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	$95.80	5.566%	$101.1322	$101.13	$101.15	$101.10
Purchase #2	$179.76	9.296%	$196.4705	$196.47	$196.45	$196.50
Purchase #3	$37.80	9.608%	$41.4318	$41.43	$41.45	$41.40
Purchase #4	$48.27	11.378%	$53.7622	$53.76	$53.75	$53.80
Purchase #5	$23.74	10.464%	$26.2242	$26.22	$26.20	$26.20
Purchase #6	$124.29	5.852%	$131.5635	$131.56	$131.55	$131.60
Purchase #7	$30.73	10.447%	$33.9404	$33.94	$33.95	$33.90
7 purchase totals =	$540.39		$584.5248	$584.51	$584.50	$584.50