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	$244.84	12.618%	$275.7339	$275.73	$275.75	$275.70
Purchase #2	$249.47	13.267%	$282.5672	$282.57	$282.55	$282.60
Purchase #3	$158.89	11.667%	$177.4277	$177.43	$177.45	$177.40
Purchase #4	$69.52	12.197%	$77.9994	$78.00	$78.00	$78.00
Purchase #5	$9.80	9.807%	$10.7611	$10.76	$10.75	$10.80
Purchase #6	$63.56	4.417%	$66.3674	$66.37	$66.35	$66.40
Purchase #7	$79.82	3.522%	$82.6313	$82.63	$82.65	$82.60
7 purchase totals =	$875.90		$973.4880	$973.49	$973.50	$973.50