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	$72.47	12.757%	$81.715	$81.72	$81.70	$81.70
Purchase #2	$69.51	4.475%	$72.6206	$72.62	$72.60	$72.60
Purchase #3	$181.33	10.658%	$200.6562	$200.66	$200.65	$200.70
Purchase #4	$144.83	3.734%	$150.238	$150.24	$150.25	$150.20
Purchase #5	$37.29	11.342%	$41.5194	$41.52	$41.50	$41.50
Purchase #6	$81.92	12.396%	$92.0748	$92.07	$92.05	$92.10
Purchase #7	$250.90	13.454%	$284.6561	$284.66	$284.65	$284.70
7 purchase totals =	$838.25		$923.4801	$923.49	$923.40	$923.50