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	$132.92	13.411%	$150.7459	$150.75	$150.75	$150.70
Purchase #2	$43.81	12.179%	$49.1456	$49.15	$49.15	$49.10
Purchase #3	$123.41	7.682%	$132.8904	$132.89	$132.90	$132.90
Purchase #4	$119.57	12.567%	$134.5964	$134.60	$134.60	$134.60
Purchase #5	$40.63	12.842%	$45.8477	$45.85	$45.85	$45.80
Purchase #6	$93.72	11.428%	$104.4303	$104.43	$104.45	$104.40
Purchase #7	$185.49	6.200%	$196.9904	$196.99	$197.00	$197.00
7 purchase totals =	$739.55		$814.6467	$814.66	$814.70	$814.50