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	$193.52	8.865%	$210.6755	$210.68	$210.70	$210.70
Purchase #2	$163.77	3.639%	$169.7296	$169.73	$169.75	$169.70
Purchase #3	$27.57	11.630%	$30.7764	$30.78	$30.80	$30.80
Purchase #4	$59.96	12.680%	$67.5629	$67.56	$67.55	$67.60
Purchase #5	$112.31	9.725%	$123.2321	$123.23	$123.25	$123.20
Purchase #6	$99.98	4.632%	$104.6111	$104.61	$104.60	$104.60
Purchase #7	$90.40	4.531%	$94.496	$94.50	$94.50	$94.50
7 purchase totals =	$747.51		$801.0836	$801.09	$801.15	$801.10