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	$246.42	6.467%	$262.356	$262.36	$262.35	$262.40
Purchase #2	$167.46	3.208%	$172.8321	$172.83	$172.85	$172.80
Purchase #3	$32.43	8.546%	$35.2015	$35.20	$35.20	$35.20
Purchase #4	$35.98	9.456%	$39.3823	$39.38	$39.40	$39.40
Purchase #5	$218.74	11.212%	$243.2651	$243.27	$243.25	$243.30
Purchase #6	$13.64	9.237%	$14.8999	$14.90	$14.90	$14.90
Purchase #7	$213.76	10.238%	$235.6447	$235.64	$235.65	$235.60
7 purchase totals =	$928.43		$1,003.5816	$1,003.58	$1,003.60	$1,003.60