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	$165.59	4.123%	$172.4173	$172.42	$172.40	$172.40
Purchase #2	$22.58	13.138%	$25.5466	$25.55	$25.55	$25.50
Purchase #3	$165.82	5.684%	$175.2452	$175.25	$175.25	$175.20
Purchase #4	$109.37	12.586%	$123.1353	$123.14	$123.15	$123.10
Purchase #5	$7.95	8.346%	$8.6135	$8.61	$8.60	$8.60
Purchase #6	$234.80	11.770%	$262.436	$262.44	$262.45	$262.40
Purchase #7	$39.48	13.709%	$44.8923	$44.89	$44.90	$44.90
7 purchase totals =	$745.59		$812.2862	$812.30	$812.30	$812.10