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	$89.56	12.402%	$100.6672	$100.67	$100.65	$100.70
Purchase #2	$191.80	10.387%	$211.7223	$211.72	$211.70	$211.70
Purchase #3	$247.48	4.685%	$259.0744	$259.07	$259.05	$259.10
Purchase #4	$43.40	7.240%	$46.5422	$46.54	$46.55	$46.50
Purchase #5	$149.29	12.181%	$167.475	$167.48	$167.50	$167.50
Purchase #6	$12.28	13.581%	$13.9477	$13.95	$13.95	$13.90
Purchase #7	$47.98	10.605%	$53.0683	$53.07	$53.05	$53.10
7 purchase totals =	$781.79		$852.4971	$852.50	$852.45	$852.50