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	$98.52	13.141%	$111.4665	$111.47	$111.45	$111.50
Purchase #2	$135.44	10.786%	$150.0486	$150.05	$150.05	$150.00
Purchase #3	$185.31	7.253%	$198.7505	$198.75	$198.75	$198.80
Purchase #4	$113.67	4.804%	$119.1307	$119.13	$119.15	$119.10
Purchase #5	$169.74	9.378%	$185.6582	$185.66	$185.65	$185.70
Purchase #6	$12.77	3.739%	$13.2475	$13.25	$13.25	$13.20
Purchase #7	$94.94	11.500%	$105.8581	$105.86	$105.85	$105.90
7 purchase totals =	$810.39		$884.1601	$884.17	$884.15	$884.20