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	$34.28	8.133%	$37.068	$37.07	$37.05	$37.10
Purchase #2	$130.29	9.354%	$142.4773	$142.48	$142.50	$142.50
Purchase #3	$28.42	13.668%	$32.3044	$32.30	$32.30	$32.30
Purchase #4	$238.88	4.863%	$250.4967	$250.50	$250.50	$250.50
Purchase #5	$244.69	5.227%	$257.4799	$257.48	$257.50	$257.50
Purchase #6	$81.43	4.868%	$85.394	$85.39	$85.40	$85.40
Purchase #7	$130.32	11.571%	$145.3993	$145.40	$145.40	$145.40
7 purchase totals =	$888.31		$950.6196	$950.62	$950.65	$950.70