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	$9.33	13.236%	$10.5649	$10.56	$10.55	$10.60
Purchase #2	$190.39	13.279%	$215.6719	$215.67	$215.65	$215.70
Purchase #3	$140.54	10.578%	$155.4063	$155.41	$155.40	$155.40
Purchase #4	$191.96	12.785%	$216.5021	$216.50	$216.50	$216.50
Purchase #5	$223.47	6.710%	$238.4648	$238.46	$238.45	$238.50
Purchase #6	$214.87	4.628%	$224.8142	$224.81	$224.80	$224.80
Purchase #7	$139.86	7.816%	$150.7915	$150.79	$150.80	$150.80
7 purchase totals =	$1,110.42		$1,212.2157	$1,212.20	$1,212.15	$1,212.30