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	$85.40	8.391%	$92.5659	$92.57	$92.55	$92.60
Purchase #2	$149.70	12.309%	$168.1266	$168.13	$168.15	$168.10
Purchase #3	$134.48	12.599%	$151.4231	$151.42	$151.40	$151.40
Purchase #4	$9.71	3.385%	$10.0387	$10.04	$10.05	$10.00
Purchase #5	$153.28	9.372%	$167.6454	$167.65	$167.65	$167.60
Purchase #6	$13.56	6.214%	$14.4026	$14.40	$14.40	$14.40
Purchase #7	$83.55	7.863%	$90.1195	$90.12	$90.10	$90.10
7 purchase totals =	$629.68		$694.3218	$694.33	$694.30	$694.20