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	$87.57	7.723%	$94.333	$94.33	$94.35	$94.30
Purchase #2	$243.52	4.525%	$254.5393	$254.54	$254.55	$254.50
Purchase #3	$30.67	4.692%	$32.109	$32.11	$32.10	$32.10
Purchase #4	$80.80	3.640%	$83.7411	$83.74	$83.75	$83.70
Purchase #5	$52.85	13.297%	$59.8775	$59.88	$59.90	$59.90
Purchase #6	$221.81	8.360%	$240.3533	$240.35	$240.35	$240.40
Purchase #7	$113.34	3.506%	$117.3137	$117.31	$117.30	$117.30
7 purchase totals =	$830.56		$882.2669	$882.26	$882.30	$882.20