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	$96.89	3.858%	$100.628	$100.63	$100.65	$100.60
Purchase #2	$135.88	5.249%	$143.0123	$143.01	$143.00	$143.00
Purchase #3	$120.82	7.773%	$130.2113	$130.21	$130.20	$130.20
Purchase #4	$75.53	8.770%	$82.154	$82.15	$82.15	$82.20
Purchase #5	$44.36	3.390%	$45.8638	$45.86	$45.85	$45.90
Purchase #6	$35.44	8.641%	$38.5024	$38.50	$38.50	$38.50
Purchase #7	$244.35	3.870%	$253.8063	$253.81	$253.80	$253.80
7 purchase totals =	$753.27		$794.1781	$794.17	$794.15	$794.20