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	$31.44	6.736%	$33.5578	$33.56	$33.55	$33.60
Purchase #2	$10.73	6.657%	$11.4443	$11.44	$11.45	$11.40
Purchase #3	$50.84	12.382%	$57.135	$57.14	$57.15	$57.10
Purchase #4	$42.88	12.537%	$48.2559	$48.26	$48.25	$48.30
Purchase #5	$98.86	12.780%	$111.4943	$111.49	$111.50	$111.50
Purchase #6	$11.78	9.172%	$12.8605	$12.86	$12.85	$12.90
Purchase #7	$96.47	9.314%	$105.4552	$105.46	$105.45	$105.50
7 purchase totals =	$343.00		$380.2030	$380.21	$380.20	$380.30