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	$208.91	13.872%	$237.89	$237.89	$237.90	$237.90
Purchase #2	$203.89	11.637%	$227.6167	$227.62	$227.60	$227.60
Purchase #3	$97.78	3.413%	$101.1172	$101.12	$101.10	$101.10
Purchase #4	$204.63	5.233%	$215.3383	$215.34	$215.35	$215.30
Purchase #5	$189.82	8.290%	$205.5561	$205.56	$205.55	$205.60
Purchase #6	$216.88	3.437%	$224.3342	$224.33	$224.35	$224.30
Purchase #7	$78.83	12.472%	$88.6617	$88.66	$88.65	$88.70
7 purchase totals =	$1,200.74		$1,300.5142	$1,300.52	$1,300.50	$1,300.50