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	$131.66	7.488%	$141.5187	$141.52	$141.50	$141.50
Purchase #2	$147.39	3.345%	$152.3202	$152.32	$152.30	$152.30
Purchase #3	$6.43	11.471%	$7.1676	$7.17	$7.15	$7.20
Purchase #4	$223.32	10.371%	$246.4805	$246.48	$246.50	$246.50
Purchase #5	$81.78	13.503%	$92.8228	$92.82	$92.80	$92.80
Purchase #6	$80.50	9.429%	$88.0903	$88.09	$88.10	$88.10
Purchase #7	$193.41	10.634%	$213.9772	$213.98	$214.00	$214.00
7 purchase totals =	$864.49		$942.3773	$942.38	$942.35	$942.40