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	$145.32	3.672%	$150.6562	$150.66	$150.65	$150.70
Purchase #2	$105.35	13.488%	$119.5596	$119.56	$119.55	$119.60
Purchase #3	$23.76	10.837%	$26.3349	$26.33	$26.35	$26.30
Purchase #4	$22.37	10.830%	$24.7927	$24.79	$24.80	$24.80
Purchase #5	$116.87	5.600%	$123.4147	$123.41	$123.40	$123.40
Purchase #6	$59.61	6.620%	$63.5562	$63.56	$63.55	$63.60
Purchase #7	$78.64	6.624%	$83.8491	$83.85	$83.85	$83.80
7 purchase totals =	$551.92		$592.1634	$592.16	$592.15	$592.20