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	$214.60	9.436%	$234.8497	$234.85	$234.85	$234.80
Purchase #2	$36.47	9.294%	$39.8595	$39.86	$39.85	$39.90
Purchase #3	$156.46	9.211%	$170.8715	$170.87	$170.85	$170.90
Purchase #4	$18.50	11.728%	$20.6697	$20.67	$20.65	$20.70
Purchase #5	$19.57	8.781%	$21.2884	$21.29	$21.30	$21.30
Purchase #6	$30.65	12.406%	$34.4524	$34.45	$34.45	$34.50
Purchase #7	$102.53	8.556%	$111.3025	$111.30	$111.30	$111.30
7 purchase totals =	$578.78		$633.2937	$633.29	$633.25	$633.40