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	$245.98	4.321%	$256.6088	$256.61	$256.60	$256.60
Purchase #2	$81.64	12.625%	$91.9471	$91.95	$91.95	$91.90
Purchase #3	$238.74	12.804%	$269.3083	$269.31	$269.30	$269.30
Purchase #4	$82.78	11.703%	$92.4677	$92.47	$92.45	$92.50
Purchase #5	$123.78	13.129%	$140.0311	$140.03	$140.05	$140.00
Purchase #6	$123.44	8.380%	$133.7843	$133.78	$133.80	$133.80
Purchase #7	$55.77	6.485%	$59.3867	$59.39	$59.40	$59.40
7 purchase totals =	$952.13		$1,043.5340	$1,043.54	$1,043.55	$1,043.50