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	$77.43	5.812%	$81.9302	$81.93	$81.95	$81.90
Purchase #2	$44.35	9.709%	$48.6559	$48.66	$48.65	$48.70
Purchase #3	$42.73	11.164%	$47.5004	$47.50	$47.50	$47.50
Purchase #4	$159.85	4.130%	$166.4518	$166.45	$166.45	$166.50
Purchase #5	$93.69	7.639%	$100.847	$100.85	$100.85	$100.80
Purchase #6	$238.34	11.363%	$265.4226	$265.42	$265.40	$265.40
Purchase #7	$27.71	13.702%	$31.5068	$31.51	$31.50	$31.50
7 purchase totals =	$684.10		$742.3147	$742.32	$742.30	$742.30