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	$134.51	7.778%	$144.9722	$144.97	$144.95	$145.00
Purchase #2	$179.53	11.673%	$200.4865	$200.49	$200.50	$200.50
Purchase #3	$178.55	12.102%	$200.1581	$200.16	$200.15	$200.20
Purchase #4	$154.34	9.171%	$168.4945	$168.49	$168.50	$168.50
Purchase #5	$101.41	12.675%	$114.2637	$114.26	$114.25	$114.30
Purchase #6	$39.84	12.668%	$44.8869	$44.89	$44.90	$44.90
Purchase #7	$170.82	5.616%	$180.4133	$180.41	$180.40	$180.40
7 purchase totals =	$959.00		$1,053.6752	$1,053.67	$1,053.65	$1,053.80