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	$211.42	13.284%	$239.505	$239.51	$239.50	$239.50
Purchase #2	$30.78	10.262%	$33.9386	$33.94	$33.95	$33.90
Purchase #3	$121.47	4.560%	$127.009	$127.01	$127.00	$127.00
Purchase #4	$39.44	11.171%	$43.8458	$43.85	$43.85	$43.80
Purchase #5	$100.36	10.511%	$110.9088	$110.91	$110.90	$110.90
Purchase #6	$67.89	6.635%	$72.3945	$72.39	$72.40	$72.40
Purchase #7	$22.76	13.175%	$25.7586	$25.76	$25.75	$25.80
7 purchase totals =	$594.12		$653.3603	$653.37	$653.35	$653.30