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	$190.77	10.200%	$210.2285	$210.23	$210.25	$210.20
Purchase #2	$123.58	11.428%	$137.7027	$137.70	$137.70	$137.70
Purchase #3	$183.64	3.641%	$190.3263	$190.33	$190.35	$190.30
Purchase #4	$28.38	13.681%	$32.2627	$32.26	$32.25	$32.30
Purchase #5	$81.63	4.487%	$85.2927	$85.29	$85.30	$85.30
Purchase #6	$143.89	12.410%	$161.7467	$161.75	$161.75	$161.70
Purchase #7	$184.81	3.371%	$191.0399	$191.04	$191.05	$191.00
7 purchase totals =	$936.70		$1,008.5995	$1,008.60	$1,008.65	$1,008.50