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	$119.96	9.242%	$131.0467	$131.05	$131.05	$131.00
Purchase #2	$102.26	10.124%	$112.6128	$112.61	$112.60	$112.60
Purchase #3	$155.31	10.430%	$171.5088	$171.51	$171.50	$171.50
Purchase #4	$94.92	10.506%	$104.8923	$104.89	$104.90	$104.90
Purchase #5	$99.49	6.471%	$105.928	$105.93	$105.95	$105.90
Purchase #6	$219.94	11.164%	$244.4941	$244.49	$244.50	$244.50
Purchase #7	$31.60	7.110%	$33.8468	$33.85	$33.85	$33.80
7 purchase totals =	$823.48		$904.3295	$904.33	$904.35	$904.20