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	$245.95	3.276%	$254.0073	$254.01	$254.00	$254.00
Purchase #2	$200.28	3.290%	$206.8692	$206.87	$206.85	$206.90
Purchase #3	$45.93	8.865%	$50.0017	$50.00	$50.00	$50.00
Purchase #4	$42.58	7.778%	$45.8919	$45.89	$45.90	$45.90
Purchase #5	$18.88	6.868%	$20.1767	$20.18	$20.20	$20.20
Purchase #6	$241.86	11.401%	$269.4345	$269.43	$269.45	$269.40
Purchase #7	$95.43	3.521%	$98.7901	$98.79	$98.80	$98.80
7 purchase totals =	$890.91		$945.1714	$945.17	$945.20	$945.20