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	$178.89	12.330%	$200.9471	$200.95	$200.95	$200.90
Purchase #2	$25.37	12.437%	$28.5253	$28.53	$28.55	$28.50
Purchase #3	$45.67	6.281%	$48.5385	$48.54	$48.55	$48.50
Purchase #4	$233.66	12.578%	$263.0498	$263.05	$263.05	$263.00
Purchase #5	$245.72	7.785%	$264.8493	$264.85	$264.85	$264.80
Purchase #6	$161.92	11.470%	$180.4922	$180.49	$180.50	$180.50
Purchase #7	$16.73	8.381%	$18.1321	$18.13	$18.15	$18.10
7 purchase totals =	$907.96		$1,004.5343	$1,004.54	$1,004.60	$1,004.30