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	$131.86	4.160%	$137.3454	$137.35	$137.35	$137.30
Purchase #2	$164.43	4.546%	$171.905	$171.91	$171.90	$171.90
Purchase #3	$196.72	8.103%	$212.6602	$212.66	$212.65	$212.70
Purchase #4	$60.33	8.593%	$65.5142	$65.51	$65.50	$65.50
Purchase #5	$179.76	13.632%	$204.2649	$204.26	$204.25	$204.30
Purchase #6	$65.37	8.236%	$70.7539	$70.75	$70.75	$70.80
Purchase #7	$109.91	7.451%	$118.0994	$118.10	$118.10	$118.10
7 purchase totals =	$908.38		$980.5430	$980.54	$980.50	$980.60