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	$119.61	12.279%	$134.2969	$134.30	$134.30	$134.30
Purchase #2	$197.39	11.670%	$220.4254	$220.43	$220.45	$220.40
Purchase #3	$231.40	10.614%	$255.9608	$255.96	$255.95	$256.00
Purchase #4	$107.81	3.118%	$111.1715	$111.17	$111.15	$111.20
Purchase #5	$162.44	3.511%	$168.1433	$168.14	$168.15	$168.10
Purchase #6	$168.57	11.333%	$187.674	$187.67	$187.65	$187.70
Purchase #7	$164.53	13.727%	$187.115	$187.12	$187.10	$187.10
7 purchase totals =	$1,151.75		$1,264.7869	$1,264.79	$1,264.75	$1,264.80