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	$41.51	11.415%	$46.2484	$46.25	$46.25	$46.20
Purchase #2	$35.59	4.207%	$37.0873	$37.09	$37.10	$37.10
Purchase #3	$211.43	4.559%	$221.0691	$221.07	$221.05	$221.10
Purchase #4	$129.66	3.462%	$134.1488	$134.15	$134.15	$134.10
Purchase #5	$119.53	6.742%	$127.5887	$127.59	$127.60	$127.60
Purchase #6	$250.84	6.569%	$267.3177	$267.32	$267.30	$267.30
Purchase #7	$84.71	4.533%	$88.5499	$88.55	$88.55	$88.50
7 purchase totals =	$873.27		$922.0099	$922.02	$922.00	$921.90