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	$192.46	3.677%	$199.5368	$199.54	$199.55	$199.50
Purchase #2	$168.25	9.732%	$184.6241	$184.62	$184.60	$184.60
Purchase #3	$55.55	11.208%	$61.776	$61.78	$61.80	$61.80
Purchase #4	$44.48	13.122%	$50.3167	$50.32	$50.30	$50.30
Purchase #5	$116.91	9.569%	$128.0971	$128.10	$128.10	$128.10
Purchase #6	$188.73	13.124%	$213.4989	$213.50	$213.50	$213.50
Purchase #7	$121.66	5.790%	$128.7041	$128.70	$128.70	$128.70
7 purchase totals =	$888.04		$966.5537	$966.56	$966.55	$966.50