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	$151.98	11.129%	$168.8939	$168.89	$168.90	$168.90
Purchase #2	$237.35	10.327%	$261.8611	$261.86	$261.85	$261.90
Purchase #3	$104.73	7.256%	$112.3292	$112.33	$112.35	$112.30
Purchase #4	$152.71	9.285%	$166.8891	$166.89	$166.90	$166.90
Purchase #5	$94.31	13.684%	$107.2154	$107.22	$107.20	$107.20
Purchase #6	$12.55	13.286%	$14.2174	$14.22	$14.20	$14.20
Purchase #7	$63.61	3.457%	$65.809	$65.81	$65.80	$65.80
7 purchase totals =	$817.24		$897.2151	$897.22	$897.20	$897.20