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	$158.52	3.485%	$164.0444	$164.04	$164.05	$164.00
Purchase #2	$199.79	3.265%	$206.3131	$206.31	$206.30	$206.30
Purchase #3	$222.64	9.123%	$242.9514	$242.95	$242.95	$243.00
Purchase #4	$248.47	6.112%	$263.6565	$263.66	$263.65	$263.70
Purchase #5	$176.51	4.196%	$183.9164	$183.92	$183.90	$183.90
Purchase #6	$114.48	11.744%	$127.9245	$127.92	$127.90	$127.90
Purchase #7	$129.27	11.724%	$144.4256	$144.43	$144.45	$144.40
7 purchase totals =	$1,249.68		$1,333.2319	$1,333.23	$1,333.20	$1,333.20