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	$76.54	12.228%	$85.8993	$85.90	$85.90	$85.90
Purchase #2	$54.63	9.547%	$59.8455	$59.85	$59.85	$59.80
Purchase #3	$32.27	4.534%	$33.7331	$33.73	$33.75	$33.70
Purchase #4	$139.25	3.769%	$144.4983	$144.50	$144.50	$144.50
Purchase #5	$71.66	8.302%	$77.6092	$77.61	$77.60	$77.60
Purchase #6	$59.57	8.175%	$64.4398	$64.44	$64.45	$64.40
Purchase #7	$28.51	4.679%	$29.844	$29.84	$29.85	$29.80
7 purchase totals =	$462.43		$495.8692	$495.87	$495.90	$495.70