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	$82.44	8.145%	$89.1547	$89.15	$89.15	$89.20
Purchase #2	$116.83	5.493%	$123.2475	$123.25	$123.25	$123.20
Purchase #3	$154.51	10.785%	$171.1739	$171.17	$171.15	$171.20
Purchase #4	$123.45	5.851%	$130.6731	$130.67	$130.65	$130.70
Purchase #5	$149.84	10.703%	$165.8774	$165.88	$165.90	$165.90
Purchase #6	$129.55	10.561%	$143.2318	$143.23	$143.25	$143.20
Purchase #7	$242.47	6.674%	$258.6524	$258.65	$258.65	$258.70
7 purchase totals =	$999.09		$1,082.0108	$1,082.00	$1,082.00	$1,082.10