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	$44.29	8.499%	$48.0542	$48.05	$48.05	$48.10
Purchase #2	$173.28	12.140%	$194.3162	$194.32	$194.30	$194.30
Purchase #3	$38.53	4.482%	$40.2569	$40.26	$40.25	$40.30
Purchase #4	$57.25	10.297%	$63.145	$63.15	$63.15	$63.10
Purchase #5	$185.35	9.796%	$203.5069	$203.51	$203.50	$203.50
Purchase #6	$63.82	12.120%	$71.555	$71.56	$71.55	$71.60
Purchase #7	$141.76	7.481%	$152.3651	$152.37	$152.35	$152.40
7 purchase totals =	$704.28		$773.1993	$773.22	$773.15	$773.30