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	$167.59	3.299%	$173.1188	$173.12	$173.10	$173.10
Purchase #2	$72.33	7.703%	$77.9016	$77.90	$77.90	$77.90
Purchase #3	$66.66	8.722%	$72.4741	$72.47	$72.45	$72.50
Purchase #4	$239.78	10.174%	$264.1752	$264.18	$264.20	$264.20
Purchase #5	$142.49	11.179%	$158.419	$158.42	$158.40	$158.40
Purchase #6	$195.50	4.720%	$204.7276	$204.73	$204.75	$204.70
Purchase #7	$75.33	10.767%	$83.4408	$83.44	$83.45	$83.40
7 purchase totals =	$959.68		$1,034.2571	$1,034.26	$1,034.25	$1,034.20