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	$166.73	10.643%	$184.4751	$184.48	$184.50	$184.50
Purchase #2	$158.38	13.561%	$179.8579	$179.86	$179.85	$179.90
Purchase #3	$151.46	11.741%	$169.2429	$169.24	$169.25	$169.20
Purchase #4	$248.97	8.293%	$269.6171	$269.62	$269.60	$269.60
Purchase #5	$176.70	11.151%	$196.4038	$196.40	$196.40	$196.40
Purchase #6	$46.74	13.169%	$52.8952	$52.90	$52.90	$52.90
Purchase #7	$73.93	10.601%	$81.7673	$81.77	$81.75	$81.80
7 purchase totals =	$1,022.91		$1,134.2593	$1,134.27	$1,134.25	$1,134.30