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	$148.56	4.696%	$155.5364	$155.54	$155.55	$155.50
Purchase #2	$147.67	4.206%	$153.881	$153.88	$153.90	$153.90
Purchase #3	$100.34	7.133%	$107.4973	$107.50	$107.50	$107.50
Purchase #4	$133.60	12.522%	$150.3294	$150.33	$150.35	$150.30
Purchase #5	$123.91	3.482%	$128.2245	$128.22	$128.20	$128.20
Purchase #6	$172.49	8.530%	$187.2034	$187.20	$187.20	$187.20
Purchase #7	$104.39	6.486%	$111.1607	$111.16	$111.15	$111.20
7 purchase totals =	$930.96		$993.8327	$993.83	$993.85	$993.80