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	$137.46	7.340%	$147.5496	$147.55	$147.55	$147.50
Purchase #2	$88.32	7.567%	$95.0032	$95.00	$95.00	$95.00
Purchase #3	$161.57	4.473%	$168.797	$168.80	$168.80	$168.80
Purchase #4	$185.50	8.228%	$200.7629	$200.76	$200.75	$200.80
Purchase #5	$61.82	7.670%	$66.5616	$66.56	$66.55	$66.60
Purchase #6	$139.41	10.632%	$154.2321	$154.23	$154.25	$154.20
Purchase #7	$70.55	13.848%	$80.3198	$80.32	$80.30	$80.30
7 purchase totals =	$844.63		$913.2262	$913.22	$913.20	$913.20