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	$85.28	5.362%	$89.8527	$89.85	$89.85	$89.90
Purchase #2	$94.98	9.263%	$103.778	$103.78	$103.80	$103.80
Purchase #3	$89.95	11.720%	$100.4921	$100.49	$100.50	$100.50
Purchase #4	$211.31	4.707%	$221.2564	$221.26	$221.25	$221.30
Purchase #5	$150.31	5.572%	$158.6853	$158.69	$158.70	$158.70
Purchase #6	$165.94	12.239%	$186.2494	$186.25	$186.25	$186.20
Purchase #7	$5.53	13.736%	$6.2896	$6.29	$6.30	$6.30
7 purchase totals =	$803.30		$866.6035	$866.61	$866.65	$866.70