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	$65.42	8.760%	$71.1508	$71.15	$71.15	$71.20
Purchase #2	$79.79	11.413%	$88.8964	$88.90	$88.90	$88.90
Purchase #3	$169.50	3.132%	$174.8087	$174.81	$174.80	$174.80
Purchase #4	$131.86	10.691%	$145.9572	$145.96	$145.95	$146.00
Purchase #5	$102.60	4.119%	$106.8261	$106.83	$106.85	$106.80
Purchase #6	$103.74	7.456%	$111.4749	$111.47	$111.45	$111.50
Purchase #7	$102.91	5.144%	$108.2037	$108.20	$108.20	$108.20
7 purchase totals =	$755.82		$807.3178	$807.32	$807.30	$807.40