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	$228.51	13.849%	$260.1563	$260.16	$260.15	$260.20
Purchase #2	$140.49	5.727%	$148.5359	$148.54	$148.55	$148.50
Purchase #3	$43.70	4.127%	$45.5035	$45.50	$45.50	$45.50
Purchase #4	$174.41	11.169%	$193.8899	$193.89	$193.90	$193.90
Purchase #5	$105.37	3.279%	$108.8251	$108.83	$108.85	$108.80
Purchase #6	$197.92	12.725%	$223.1053	$223.11	$223.10	$223.10
Purchase #7	$94.97	12.271%	$106.6238	$106.62	$106.60	$106.60
7 purchase totals =	$985.37		$1,086.6398	$1,086.65	$1,086.65	$1,086.60