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	$189.55	3.691%	$196.5463	$196.55	$196.55	$196.50
Purchase #2	$161.26	12.724%	$181.7787	$181.78	$181.80	$181.80
Purchase #3	$131.95	7.715%	$142.1299	$142.13	$142.15	$142.10
Purchase #4	$162.75	10.164%	$179.2919	$179.29	$179.30	$179.30
Purchase #5	$170.83	11.422%	$190.3422	$190.34	$190.35	$190.30
Purchase #6	$137.36	9.292%	$150.1235	$150.12	$150.10	$150.10
Purchase #7	$246.72	8.761%	$268.3351	$268.34	$268.35	$268.30
7 purchase totals =	$1,200.42		$1,308.5476	$1,308.55	$1,308.60	$1,308.40