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	$182.89	4.161%	$190.5001	$190.50	$190.50	$190.50
Purchase #2	$111.37	5.472%	$117.4642	$117.46	$117.45	$117.50
Purchase #3	$88.46	12.705%	$99.6988	$99.70	$99.70	$99.70
Purchase #4	$131.40	6.872%	$140.4298	$140.43	$140.45	$140.40
Purchase #5	$67.82	4.536%	$70.8963	$70.90	$70.90	$70.90
Purchase #6	$72.37	12.661%	$81.5328	$81.53	$81.55	$81.50
Purchase #7	$83.91	4.569%	$87.7438	$87.74	$87.75	$87.70
7 purchase totals =	$738.22		$788.2658	$788.26	$788.30	$788.20