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	$213.86	4.569%	$223.6313	$223.63	$223.65	$223.60
Purchase #2	$242.41	5.782%	$256.4261	$256.43	$256.45	$256.40
Purchase #3	$97.79	6.162%	$103.8158	$103.82	$103.80	$103.80
Purchase #4	$89.48	13.185%	$101.2779	$101.28	$101.30	$101.30
Purchase #5	$154.67	7.869%	$166.841	$166.84	$166.85	$166.80
Purchase #6	$71.88	7.527%	$77.2904	$77.29	$77.30	$77.30
Purchase #7	$78.50	6.713%	$83.7697	$83.77	$83.75	$83.80
7 purchase totals =	$948.59		$1,013.0522	$1,013.06	$1,013.10	$1,013.00