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	$141.61	6.727%	$151.1361	$151.14	$151.15	$151.10
Purchase #2	$80.56	11.391%	$89.7366	$89.74	$89.75	$89.70
Purchase #3	$169.75	3.361%	$175.4553	$175.46	$175.45	$175.50
Purchase #4	$182.54	4.752%	$191.2143	$191.21	$191.20	$191.20
Purchase #5	$175.97	11.505%	$196.2153	$196.22	$196.20	$196.20
Purchase #6	$35.98	5.762%	$38.0532	$38.05	$38.05	$38.10
Purchase #7	$235.40	6.547%	$250.8116	$250.81	$250.80	$250.80
7 purchase totals =	$1,021.81		$1,092.6224	$1,092.63	$1,092.60	$1,092.60