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	$116.57	4.302%	$121.5848	$121.58	$121.60	$121.60
Purchase #2	$54.27	5.535%	$57.2738	$57.27	$57.25	$57.30
Purchase #3	$16.41	12.567%	$18.4722	$18.47	$18.45	$18.50
Purchase #4	$145.38	12.864%	$164.0817	$164.08	$164.10	$164.10
Purchase #5	$250.25	10.178%	$275.7204	$275.72	$275.70	$275.70
Purchase #6	$124.59	13.704%	$141.6638	$141.66	$141.65	$141.70
Purchase #7	$225.26	5.543%	$237.7462	$237.75	$237.75	$237.70
7 purchase totals =	$932.73		$1,016.5429	$1,016.53	$1,016.50	$1,016.60