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	$31.84	12.865%	$35.9362	$35.94	$35.95	$35.90
Purchase #2	$128.33	10.300%	$141.548	$141.55	$141.55	$141.50
Purchase #3	$131.50	10.421%	$145.2036	$145.20	$145.20	$145.20
Purchase #4	$32.59	7.840%	$35.1451	$35.15	$35.15	$35.10
Purchase #5	$100.91	3.427%	$104.3682	$104.37	$104.35	$104.40
Purchase #6	$176.39	7.175%	$189.046	$189.05	$189.05	$189.00
Purchase #7	$102.89	4.610%	$107.6332	$107.63	$107.65	$107.60
7 purchase totals =	$704.45		$758.8803	$758.89	$758.90	$758.70