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	$79.54	9.465%	$87.0685	$87.07	$87.05	$87.10
Purchase #2	$217.77	11.459%	$242.7243	$242.72	$242.70	$242.70
Purchase #3	$153.79	7.588%	$165.4596	$165.46	$165.45	$165.50
Purchase #4	$29.90	12.797%	$33.7263	$33.73	$33.75	$33.70
Purchase #5	$230.59	5.296%	$242.802	$242.80	$242.80	$242.80
Purchase #6	$43.71	3.816%	$45.378	$45.38	$45.40	$45.40
Purchase #7	$236.59	7.295%	$253.8492	$253.85	$253.85	$253.80
7 purchase totals =	$991.89		$1,071.0079	$1,071.01	$1,071.00	$1,071.00