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	$198.26	7.842%	$213.8075	$213.81	$213.80	$213.80
Purchase #2	$247.44	3.500%	$256.1004	$256.10	$256.10	$256.10
Purchase #3	$172.32	10.677%	$190.7186	$190.72	$190.70	$190.70
Purchase #4	$90.50	6.576%	$96.4513	$96.45	$96.45	$96.50
Purchase #5	$112.92	11.103%	$125.4575	$125.46	$125.45	$125.50
Purchase #6	$178.28	5.691%	$188.4259	$188.43	$188.45	$188.40
Purchase #7	$72.96	10.847%	$80.874	$80.87	$80.85	$80.90
7 purchase totals =	$1,072.68		$1,151.8352	$1,151.84	$1,151.80	$1,151.90