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	$85.89	4.373%	$89.646	$89.65	$89.65	$89.60
Purchase #2	$141.52	6.746%	$151.0669	$151.07	$151.05	$151.10
Purchase #3	$67.29	11.517%	$75.0398	$75.04	$75.05	$75.00
Purchase #4	$167.44	5.682%	$176.9539	$176.95	$176.95	$177.00
Purchase #5	$123.41	6.299%	$131.1836	$131.18	$131.20	$131.20
Purchase #6	$128.49	6.271%	$136.5476	$136.55	$136.55	$136.50
Purchase #7	$98.36	8.228%	$106.4531	$106.45	$106.45	$106.50
7 purchase totals =	$812.40		$866.8909	$866.89	$866.90	$866.90