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	$166.55	7.783%	$179.5126	$179.51	$179.50	$179.50
Purchase #2	$56.68	3.698%	$58.776	$58.78	$58.80	$58.80
Purchase #3	$156.79	5.767%	$165.8321	$165.83	$165.85	$165.80
Purchase #4	$69.58	13.478%	$78.958	$78.96	$78.95	$79.00
Purchase #5	$88.73	4.428%	$92.659	$92.66	$92.65	$92.70
Purchase #6	$84.86	11.407%	$94.54	$94.54	$94.55	$94.50
Purchase #7	$46.72	11.182%	$51.9442	$51.94	$51.95	$51.90
7 purchase totals =	$669.91		$722.2219	$722.22	$722.25	$722.20