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	$245.60	8.502%	$266.4809	$266.48	$266.50	$266.50
Purchase #2	$246.78	9.366%	$269.8934	$269.89	$269.90	$269.90
Purchase #3	$132.82	10.396%	$146.628	$146.63	$146.65	$146.60
Purchase #4	$204.70	10.872%	$226.955	$226.96	$226.95	$227.00
Purchase #5	$16.50	3.282%	$17.0415	$17.04	$17.05	$17.00
Purchase #6	$99.29	12.459%	$111.6605	$111.66	$111.65	$111.70
Purchase #7	$52.59	12.872%	$59.3594	$59.36	$59.35	$59.40
7 purchase totals =	$998.28		$1,098.0187	$1,098.02	$1,098.05	$1,098.10