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	$199.40	9.651%	$218.6441	$218.64	$218.65	$218.60
Purchase #2	$99.32	13.153%	$112.3836	$112.38	$112.40	$112.40
Purchase #3	$29.76	11.273%	$33.1148	$33.11	$33.10	$33.10
Purchase #4	$124.79	5.576%	$131.7483	$131.75	$131.75	$131.70
Purchase #5	$209.60	5.412%	$220.9436	$220.94	$220.95	$220.90
Purchase #6	$188.85	10.746%	$209.1438	$209.14	$209.15	$209.10
Purchase #7	$161.75	11.149%	$179.7835	$179.78	$179.80	$179.80
7 purchase totals =	$1,013.47		$1,105.7617	$1,105.74	$1,105.80	$1,105.60