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	$223.82	4.164%	$233.1399	$233.14	$233.15	$233.10
Purchase #2	$58.33	9.388%	$63.806	$63.81	$63.80	$63.80
Purchase #3	$175.52	5.275%	$184.7787	$184.78	$184.80	$184.80
Purchase #4	$131.75	4.380%	$137.5207	$137.52	$137.50	$137.50
Purchase #5	$216.33	11.506%	$241.2209	$241.22	$241.20	$241.20
Purchase #6	$39.88	4.486%	$41.669	$41.67	$41.65	$41.70
Purchase #7	$228.75	9.321%	$250.0718	$250.07	$250.05	$250.10
7 purchase totals =	$1,074.38		$1,152.2070	$1,152.21	$1,152.15	$1,152.20