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	$212.76	4.731%	$222.8257	$222.83	$222.85	$222.80
Purchase #2	$140.73	4.179%	$146.6111	$146.61	$146.60	$146.60
Purchase #3	$82.31	13.133%	$93.1198	$93.12	$93.10	$93.10
Purchase #4	$113.94	8.520%	$123.6477	$123.65	$123.65	$123.60
Purchase #5	$21.90	8.699%	$23.8051	$23.81	$23.80	$23.80
Purchase #6	$43.89	11.701%	$49.0256	$49.03	$49.05	$49.00
Purchase #7	$67.62	7.804%	$72.8971	$72.90	$72.90	$72.90
7 purchase totals =	$683.15		$731.9321	$731.95	$731.95	$731.80