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	$187.50	13.714%	$213.2138	$213.21	$213.20	$213.20
Purchase #2	$107.71	5.784%	$113.9399	$113.94	$113.95	$113.90
Purchase #3	$133.38	13.653%	$151.5904	$151.59	$151.60	$151.60
Purchase #4	$74.86	4.222%	$78.0206	$78.02	$78.00	$78.00
Purchase #5	$18.90	12.234%	$21.2122	$21.21	$21.20	$21.20
Purchase #6	$125.27	7.552%	$134.7304	$134.73	$134.75	$134.70
Purchase #7	$203.89	11.792%	$227.9327	$227.93	$227.95	$227.90
7 purchase totals =	$851.51		$940.6400	$940.63	$940.65	$940.50