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	$188.79	13.227%	$213.7613	$213.76	$213.75	$213.80
Purchase #2	$62.61	4.502%	$65.4287	$65.43	$65.45	$65.40
Purchase #3	$34.58	8.441%	$37.4989	$37.50	$37.50	$37.50
Purchase #4	$154.76	7.468%	$166.3175	$166.32	$166.30	$166.30
Purchase #5	$228.60	7.293%	$245.2718	$245.27	$245.25	$245.30
Purchase #6	$112.78	12.308%	$126.661	$126.66	$126.65	$126.70
Purchase #7	$146.74	8.216%	$158.7962	$158.80	$158.80	$158.80
7 purchase totals =	$928.86		$1,013.7354	$1,013.74	$1,013.70	$1,013.80