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	$183.75	8.575%	$199.5066	$199.51	$199.50	$199.50
Purchase #2	$133.58	11.465%	$148.8949	$148.89	$148.90	$148.90
Purchase #3	$128.65	5.496%	$135.7206	$135.72	$135.70	$135.70
Purchase #4	$109.46	8.756%	$119.0443	$119.04	$119.05	$119.00
Purchase #5	$98.33	7.693%	$105.8945	$105.89	$105.90	$105.90
Purchase #6	$96.74	4.528%	$101.1204	$101.12	$101.10	$101.10
Purchase #7	$212.89	4.377%	$222.2082	$222.21	$222.20	$222.20
7 purchase totals =	$963.40		$1,032.3895	$1,032.38	$1,032.35	$1,032.30