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	$87.60	11.193%	$97.4051	$97.41	$97.40	$97.40
Purchase #2	$10.33	5.188%	$10.8659	$10.87	$10.85	$10.90
Purchase #3	$18.29	3.307%	$18.8949	$18.89	$18.90	$18.90
Purchase #4	$97.86	11.414%	$109.0297	$109.03	$109.05	$109.00
Purchase #5	$59.90	4.760%	$62.7512	$62.75	$62.75	$62.80
Purchase #6	$148.76	4.340%	$155.2162	$155.22	$155.20	$155.20
Purchase #7	$76.45	5.445%	$80.6127	$80.61	$80.60	$80.60
7 purchase totals =	$499.19		$534.7757	$534.78	$534.75	$534.80