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	$170.48	4.580%	$178.288	$178.29	$178.30	$178.30
Purchase #2	$100.27	5.193%	$105.477	$105.48	$105.50	$105.50
Purchase #3	$56.56	5.133%	$59.4632	$59.46	$59.45	$59.50
Purchase #4	$197.89	9.547%	$216.7826	$216.78	$216.80	$216.80
Purchase #5	$137.45	3.320%	$142.0133	$142.01	$142.00	$142.00
Purchase #6	$116.43	8.825%	$126.7049	$126.70	$126.70	$126.70
Purchase #7	$111.80	13.414%	$126.7969	$126.80	$126.80	$126.80
7 purchase totals =	$890.88		$955.5259	$955.52	$955.55	$955.60