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	$220.46	13.678%	$250.6145	$250.61	$250.60	$250.60
Purchase #2	$20.74	3.348%	$21.4344	$21.43	$21.45	$21.40
Purchase #3	$88.79	6.363%	$94.4397	$94.44	$94.45	$94.40
Purchase #4	$250.94	10.711%	$277.8182	$277.82	$277.80	$277.80
Purchase #5	$35.87	13.396%	$40.6751	$40.68	$40.70	$40.70
Purchase #6	$239.73	13.263%	$271.5254	$271.53	$271.55	$271.50
Purchase #7	$75.28	10.826%	$83.4298	$83.43	$83.45	$83.40
7 purchase totals =	$931.81		$1,039.9371	$1,039.94	$1,040.00	$1,039.80