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	$186.69	13.543%	$211.9734	$211.97	$211.95	$212.00
Purchase #2	$129.52	11.652%	$144.6117	$144.61	$144.60	$144.60
Purchase #3	$118.29	5.229%	$124.4754	$124.48	$124.50	$124.50
Purchase #4	$119.44	6.222%	$126.8716	$126.87	$126.85	$126.90
Purchase #5	$85.72	6.815%	$91.5618	$91.56	$91.55	$91.60
Purchase #6	$5.50	6.229%	$5.8426	$5.84	$5.85	$5.80
Purchase #7	$48.50	12.460%	$54.5431	$54.54	$54.55	$54.50
7 purchase totals =	$693.66		$759.8796	$759.87	$759.85	$759.90