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	$234.71	3.242%	$242.3193	$242.32	$242.30	$242.30
Purchase #2	$208.46	5.496%	$219.917	$219.92	$219.90	$219.90
Purchase #3	$13.59	8.648%	$14.7653	$14.77	$14.75	$14.80
Purchase #4	$75.46	9.494%	$82.6242	$82.62	$82.60	$82.60
Purchase #5	$165.54	4.701%	$173.322	$173.32	$173.30	$173.30
Purchase #6	$114.32	10.597%	$126.4345	$126.43	$126.45	$126.40
Purchase #7	$223.49	11.740%	$249.7277	$249.73	$249.75	$249.70
7 purchase totals =	$1,035.57		$1,109.1100	$1,109.11	$1,109.05	$1,109.00