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	$121.55	9.111%	$132.6244	$132.62	$132.60	$132.60
Purchase #2	$154.90	11.443%	$172.6252	$172.63	$172.65	$172.60
Purchase #3	$131.28	6.344%	$139.6084	$139.61	$139.60	$139.60
Purchase #4	$39.36	11.868%	$44.0312	$44.03	$44.05	$44.00
Purchase #5	$79.48	12.748%	$89.6121	$89.61	$89.60	$89.60
Purchase #6	$238.67	10.294%	$263.2387	$263.24	$263.25	$263.20
Purchase #7	$250.71	4.615%	$262.2803	$262.28	$262.30	$262.30
7 purchase totals =	$1,015.95		$1,104.0203	$1,104.02	$1,104.05	$1,103.90