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	$54.92	10.470%	$60.6701	$60.67	$60.65	$60.70
Purchase #2	$206.73	7.308%	$221.8378	$221.84	$221.85	$221.80
Purchase #3	$195.89	13.591%	$222.5134	$222.51	$222.50	$222.50
Purchase #4	$20.76	10.543%	$22.9487	$22.95	$22.95	$22.90
Purchase #5	$57.88	13.705%	$65.8125	$65.81	$65.80	$65.80
Purchase #6	$10.27	3.604%	$10.6401	$10.64	$10.65	$10.60
Purchase #7	$42.86	11.591%	$47.8279	$47.83	$47.85	$47.80
7 purchase totals =	$589.31		$652.2505	$652.25	$652.25	$652.10