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	$40.52	13.349%	$45.929	$45.93	$45.95	$45.90
Purchase #2	$157.76	13.640%	$179.2785	$179.28	$179.30	$179.30
Purchase #3	$71.30	9.737%	$78.2425	$78.24	$78.25	$78.20
Purchase #4	$208.71	10.797%	$231.2444	$231.24	$231.25	$231.20
Purchase #5	$31.99	10.560%	$35.3681	$35.37	$35.35	$35.40
Purchase #6	$60.82	4.802%	$63.7406	$63.74	$63.75	$63.70
Purchase #7	$200.82	10.525%	$221.9563	$221.96	$221.95	$222.00
7 purchase totals =	$771.92		$855.7594	$855.76	$855.80	$855.70