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	$221.28	7.848%	$238.6461	$238.65	$238.65	$238.60
Purchase #2	$166.54	10.642%	$184.2632	$184.26	$184.25	$184.30
Purchase #3	$30.96	13.459%	$35.1269	$35.13	$35.15	$35.10
Purchase #4	$195.57	13.807%	$222.5723	$222.57	$222.55	$222.60
Purchase #5	$219.40	8.699%	$238.4856	$238.49	$238.50	$238.50
Purchase #6	$61.32	5.825%	$64.8919	$64.89	$64.90	$64.90
Purchase #7	$121.97	7.715%	$131.38	$131.38	$131.40	$131.40
7 purchase totals =	$1,017.04		$1,115.3660	$1,115.37	$1,115.40	$1,115.40