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	$100.55	8.474%	$109.0706	$109.07	$109.05	$109.10
Purchase #2	$47.64	8.235%	$51.5632	$51.56	$51.55	$51.60
Purchase #3	$124.26	3.522%	$128.6364	$128.64	$128.65	$128.60
Purchase #4	$123.49	4.417%	$128.9446	$128.94	$128.95	$128.90
Purchase #5	$29.66	13.223%	$33.5819	$33.58	$33.60	$33.60
Purchase #6	$139.31	11.760%	$155.6929	$155.69	$155.70	$155.70
Purchase #7	$77.66	9.464%	$85.0097	$85.01	$85.00	$85.00
7 purchase totals =	$642.57		$692.4993	$692.49	$692.50	$692.50