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	$143.67	6.370%	$152.8218	$152.82	$152.80	$152.80
Purchase #2	$100.35	9.501%	$109.8843	$109.88	$109.90	$109.90
Purchase #3	$63.63	8.468%	$69.0182	$69.02	$69.00	$69.00
Purchase #4	$40.52	4.222%	$42.2308	$42.23	$42.25	$42.20
Purchase #5	$242.46	13.410%	$274.9739	$274.97	$274.95	$275.00
Purchase #6	$198.63	6.827%	$212.1905	$212.19	$212.20	$212.20
Purchase #7	$80.64	13.281%	$91.3498	$91.35	$91.35	$91.30
7 purchase totals =	$869.90		$952.4693	$952.46	$952.45	$952.40