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	$155.64	7.549%	$167.3893	$167.39	$167.40	$167.40
Purchase #2	$35.26	5.816%	$37.3107	$37.31	$37.30	$37.30
Purchase #3	$207.45	7.703%	$223.4299	$223.43	$223.45	$223.40
Purchase #4	$63.51	13.639%	$72.1721	$72.17	$72.15	$72.20
Purchase #5	$126.84	3.473%	$131.2452	$131.25	$131.25	$131.20
Purchase #6	$83.48	5.332%	$87.9312	$87.93	$87.95	$87.90
Purchase #7	$68.61	10.836%	$76.0446	$76.04	$76.05	$76.00
7 purchase totals =	$740.79		$795.5230	$795.52	$795.55	$795.40