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	$100.57	3.545%	$104.1352	$104.14	$104.15	$104.10
Purchase #2	$156.26	10.128%	$172.086	$172.09	$172.10	$172.10
Purchase #3	$185.53	9.572%	$203.2889	$203.29	$203.30	$203.30
Purchase #4	$239.73	6.594%	$255.5378	$255.54	$255.55	$255.50
Purchase #5	$118.25	11.133%	$131.4148	$131.41	$131.40	$131.40
Purchase #6	$183.31	7.722%	$197.4652	$197.47	$197.45	$197.50
Purchase #7	$29.56	6.430%	$31.4607	$31.46	$31.45	$31.50
7 purchase totals =	$1,013.21		$1,095.3886	$1,095.40	$1,095.40	$1,095.40