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	$181.88	4.612%	$190.2683	$190.27	$190.25	$190.30
Purchase #2	$162.82	5.759%	$172.1968	$172.20	$172.20	$172.20
Purchase #3	$110.99	12.730%	$125.119	$125.12	$125.10	$125.10
Purchase #4	$33.52	6.272%	$35.6224	$35.62	$35.60	$35.60
Purchase #5	$124.83	11.531%	$139.2241	$139.22	$139.20	$139.20
Purchase #6	$247.31	7.445%	$265.7222	$265.72	$265.70	$265.70
Purchase #7	$63.42	13.256%	$71.827	$71.83	$71.85	$71.80
7 purchase totals =	$924.77		$999.9798	$999.98	$999.90	$999.90