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	$35.95	3.447%	$37.1892	$37.19	$37.20	$37.20
Purchase #2	$90.77	4.315%	$94.6867	$94.69	$94.70	$94.70
Purchase #3	$164.84	4.618%	$172.4523	$172.45	$172.45	$172.50
Purchase #4	$155.43	12.405%	$174.7111	$174.71	$174.70	$174.70
Purchase #5	$14.67	4.373%	$15.3115	$15.31	$15.30	$15.30
Purchase #6	$19.57	6.279%	$20.7988	$20.80	$20.80	$20.80
Purchase #7	$215.81	4.413%	$225.3337	$225.33	$225.35	$225.30
7 purchase totals =	$697.04		$740.4833	$740.48	$740.50	$740.50