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	$66.47	6.506%	$70.7945	$70.79	$70.80	$70.80
Purchase #2	$115.82	7.708%	$124.7474	$124.75	$124.75	$124.70
Purchase #3	$95.89	3.772%	$99.507	$99.51	$99.50	$99.50
Purchase #4	$57.68	6.576%	$61.473	$61.47	$61.45	$61.50
Purchase #5	$196.36	12.720%	$221.337	$221.34	$221.35	$221.30
Purchase #6	$231.52	5.745%	$244.8208	$244.82	$244.80	$244.80
Purchase #7	$47.78	8.372%	$51.7801	$51.78	$51.80	$51.80
7 purchase totals =	$811.52		$874.4598	$874.46	$874.45	$874.40