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	$114.59	13.659%	$130.2418	$130.24	$130.25	$130.20
Purchase #2	$212.35	13.399%	$240.8028	$240.80	$240.80	$240.80
Purchase #3	$91.83	12.823%	$103.6054	$103.61	$103.60	$103.60
Purchase #4	$220.81	10.172%	$243.2708	$243.27	$243.25	$243.30
Purchase #5	$47.94	6.300%	$50.9602	$50.96	$50.95	$51.00
Purchase #6	$161.53	13.617%	$183.5255	$183.53	$183.55	$183.50
Purchase #7	$99.62	4.854%	$104.4556	$104.46	$104.45	$104.50
7 purchase totals =	$948.67		$1,056.8621	$1,056.87	$1,056.85	$1,056.90