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	$248.80	5.334%	$262.071	$262.07	$262.05	$262.10
Purchase #2	$174.46	8.332%	$188.996	$189.00	$189.00	$189.00
Purchase #3	$83.89	6.233%	$89.1189	$89.12	$89.10	$89.10
Purchase #4	$246.34	11.797%	$275.4007	$275.40	$275.40	$275.40
Purchase #5	$143.46	5.216%	$150.9429	$150.94	$150.95	$150.90
Purchase #6	$38.90	11.847%	$43.5085	$43.51	$43.50	$43.50
Purchase #7	$195.31	11.592%	$217.9503	$217.95	$217.95	$218.00
7 purchase totals =	$1,131.16		$1,227.9883	$1,227.99	$1,227.95	$1,228.00