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	$166.85	8.317%	$180.7269	$180.73	$180.75	$180.70
Purchase #2	$241.39	9.398%	$264.0758	$264.08	$264.10	$264.10
Purchase #3	$30.27	12.851%	$34.16	$34.16	$34.15	$34.20
Purchase #4	$52.27	13.827%	$59.4974	$59.50	$59.50	$59.50
Purchase #5	$154.64	11.679%	$172.7004	$172.70	$172.70	$172.70
Purchase #6	$126.71	13.425%	$143.7208	$143.72	$143.70	$143.70
Purchase #7	$139.90	11.609%	$156.141	$156.14	$156.15	$156.10
7 purchase totals =	$912.03		$1,011.0223	$1,011.03	$1,011.05	$1,011.00