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	$53.32	3.194%	$55.023	$55.02	$55.00	$55.00
Purchase #2	$244.44	13.792%	$278.1532	$278.15	$278.15	$278.20
Purchase #3	$154.66	6.295%	$164.3958	$164.40	$164.40	$164.40
Purchase #4	$161.26	6.483%	$171.7145	$171.71	$171.70	$171.70
Purchase #5	$160.62	7.495%	$172.6585	$172.66	$172.65	$172.70
Purchase #6	$93.48	8.557%	$101.4791	$101.48	$101.50	$101.50
Purchase #7	$53.44	12.166%	$59.9415	$59.94	$59.95	$59.90
7 purchase totals =	$921.22		$1,003.3656	$1,003.36	$1,003.35	$1,003.40