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	$217.45	12.428%	$244.4747	$244.47	$244.45	$244.50
Purchase #2	$42.91	10.744%	$47.5203	$47.52	$47.50	$47.50
Purchase #3	$240.34	12.147%	$269.5341	$269.53	$269.55	$269.50
Purchase #4	$63.78	7.303%	$68.4379	$68.44	$68.45	$68.40
Purchase #5	$194.60	11.236%	$216.4653	$216.47	$216.45	$216.50
Purchase #6	$72.56	11.806%	$81.1264	$81.13	$81.15	$81.10
Purchase #7	$229.42	4.627%	$240.0353	$240.04	$240.05	$240.00
7 purchase totals =	$1,061.06		$1,167.5940	$1,167.60	$1,167.60	$1,167.50