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	$82.52	11.499%	$92.009	$92.01	$92.00	$92.00
Purchase #2	$215.33	7.557%	$231.6025	$231.60	$231.60	$231.60
Purchase #3	$230.86	8.431%	$250.3238	$250.32	$250.30	$250.30
Purchase #4	$73.30	12.864%	$82.7293	$82.73	$82.75	$82.70
Purchase #5	$150.29	10.367%	$165.8706	$165.87	$165.85	$165.90
Purchase #6	$43.40	5.758%	$45.899	$45.90	$45.90	$45.90
Purchase #7	$59.63	11.436%	$66.4493	$66.45	$66.45	$66.40
7 purchase totals =	$855.33		$934.8835	$934.88	$934.85	$934.80