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	$70.73	3.183%	$72.9813	$72.98	$73.00	$73.00
Purchase #2	$126.59	13.297%	$143.4227	$143.42	$143.40	$143.40
Purchase #3	$221.42	11.465%	$246.8058	$246.81	$246.80	$246.80
Purchase #4	$155.27	11.166%	$172.6074	$172.61	$172.60	$172.60
Purchase #5	$198.83	6.757%	$212.2649	$212.26	$212.25	$212.30
Purchase #6	$119.26	6.817%	$127.39	$127.39	$127.40	$127.40
Purchase #7	$212.92	11.820%	$238.0871	$238.09	$238.10	$238.10
7 purchase totals =	$1,105.02		$1,213.5592	$1,213.56	$1,213.55	$1,213.60