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	$135.42	5.491%	$142.8559	$142.86	$142.85	$142.90
Purchase #2	$183.54	4.439%	$191.6873	$191.69	$191.70	$191.70
Purchase #3	$24.83	5.626%	$26.2269	$26.23	$26.25	$26.20
Purchase #4	$146.94	3.790%	$152.509	$152.51	$152.50	$152.50
Purchase #5	$139.99	11.360%	$155.8929	$155.89	$155.90	$155.90
Purchase #6	$33.58	12.698%	$37.844	$37.84	$37.85	$37.80
Purchase #7	$78.56	4.192%	$81.8532	$81.85	$81.85	$81.90
7 purchase totals =	$742.86		$788.8692	$788.87	$788.90	$788.90