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	$67.73	6.408%	$72.0701	$72.07	$72.05	$72.10
Purchase #2	$84.41	13.746%	$96.013	$96.01	$96.00	$96.00
Purchase #3	$84.40	4.418%	$88.1288	$88.13	$88.15	$88.10
Purchase #4	$176.82	9.839%	$194.2173	$194.22	$194.20	$194.20
Purchase #5	$152.71	8.143%	$165.1452	$165.15	$165.15	$165.10
Purchase #6	$192.61	9.817%	$211.5185	$211.52	$211.50	$211.50
Purchase #7	$74.49	6.612%	$79.4153	$79.42	$79.40	$79.40
7 purchase totals =	$833.17		$906.5082	$906.52	$906.45	$906.40