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	$193.35	10.508%	$213.6672	$213.67	$213.65	$213.70
Purchase #2	$95.52	8.143%	$103.2982	$103.30	$103.30	$103.30
Purchase #3	$16.53	10.338%	$18.2389	$18.24	$18.25	$18.20
Purchase #4	$78.89	12.234%	$88.5414	$88.54	$88.55	$88.50
Purchase #5	$57.49	12.345%	$64.5871	$64.59	$64.60	$64.60
Purchase #6	$67.71	12.847%	$76.4087	$76.41	$76.40	$76.40
Purchase #7	$94.70	6.356%	$100.7191	$100.72	$100.70	$100.70
7 purchase totals =	$604.19		$665.4606	$665.47	$665.45	$665.40