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	$39.32	6.644%	$41.9324	$41.93	$41.95	$41.90
Purchase #2	$214.61	7.739%	$231.2187	$231.22	$231.20	$231.20
Purchase #3	$111.74	11.124%	$124.17	$124.17	$124.15	$124.20
Purchase #4	$185.38	8.136%	$200.4625	$200.46	$200.45	$200.50
Purchase #5	$59.56	3.182%	$61.4552	$61.46	$61.45	$61.50
Purchase #6	$63.61	12.755%	$71.7235	$71.72	$71.70	$71.70
Purchase #7	$96.83	8.693%	$105.2474	$105.25	$105.25	$105.20
7 purchase totals =	$771.05		$836.2097	$836.21	$836.15	$836.20