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	$209.64	3.669%	$217.3317	$217.33	$217.35	$217.30
Purchase #2	$88.49	9.167%	$96.6019	$96.60	$96.60	$96.60
Purchase #3	$242.82	9.226%	$265.2226	$265.22	$265.20	$265.20
Purchase #4	$165.67	13.220%	$187.5716	$187.57	$187.55	$187.60
Purchase #5	$101.86	3.260%	$105.1806	$105.18	$105.20	$105.20
Purchase #6	$127.61	5.743%	$134.9386	$134.94	$134.95	$134.90
Purchase #7	$139.95	8.693%	$152.1159	$152.12	$152.10	$152.10
7 purchase totals =	$1,076.04		$1,158.9629	$1,158.96	$1,158.95	$1,158.90