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	$147.62	9.385%	$161.4741	$161.47	$161.45	$161.50
Purchase #2	$214.82	4.143%	$223.72	$223.72	$223.70	$223.70
Purchase #3	$15.82	9.254%	$17.284	$17.28	$17.30	$17.30
Purchase #4	$203.28	9.327%	$222.2399	$222.24	$222.25	$222.20
Purchase #5	$35.79	10.390%	$39.5086	$39.51	$39.50	$39.50
Purchase #6	$123.28	4.281%	$128.5576	$128.56	$128.55	$128.60
Purchase #7	$249.93	9.361%	$273.3259	$273.33	$273.35	$273.30
7 purchase totals =	$990.54		$1,066.1101	$1,066.11	$1,066.10	$1,066.10