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	$32.54	8.355%	$35.2587	$35.26	$35.25	$35.30
Purchase #2	$250.45	13.169%	$283.4318	$283.43	$283.45	$283.40
Purchase #3	$127.59	13.550%	$144.8784	$144.88	$144.90	$144.90
Purchase #4	$76.41	9.584%	$83.7331	$83.73	$83.75	$83.70
Purchase #5	$159.92	12.763%	$180.3306	$180.33	$180.35	$180.30
Purchase #6	$90.87	8.496%	$98.5903	$98.59	$98.60	$98.60
Purchase #7	$108.57	9.123%	$118.4748	$118.47	$118.45	$118.50
7 purchase totals =	$846.35		$944.6977	$944.69	$944.75	$944.70