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	$63.38	4.753%	$66.3925	$66.39	$66.40	$66.40
Purchase #2	$194.72	8.253%	$210.7902	$210.79	$210.80	$210.80
Purchase #3	$148.36	13.728%	$168.7269	$168.73	$168.75	$168.70
Purchase #4	$110.78	11.617%	$123.6493	$123.65	$123.65	$123.60
Purchase #5	$152.95	5.768%	$161.7722	$161.77	$161.75	$161.80
Purchase #6	$178.82	3.105%	$184.3724	$184.37	$184.35	$184.40
Purchase #7	$217.58	12.676%	$245.1604	$245.16	$245.15	$245.20
7 purchase totals =	$1,066.59		$1,160.8639	$1,160.86	$1,160.85	$1,160.90