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	$210.43	13.800%	$239.4693	$239.47	$239.45	$239.50
Purchase #2	$81.86	11.783%	$91.5056	$91.51	$91.50	$91.50
Purchase #3	$60.78	6.797%	$64.9112	$64.91	$64.90	$64.90
Purchase #4	$32.55	3.586%	$33.7172	$33.72	$33.70	$33.70
Purchase #5	$102.39	10.172%	$112.8051	$112.81	$112.80	$112.80
Purchase #6	$90.79	13.785%	$103.3054	$103.31	$103.30	$103.30
Purchase #7	$226.33	6.573%	$241.2067	$241.21	$241.20	$241.20
7 purchase totals =	$805.13		$886.9205	$886.94	$886.85	$886.90