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	$93.64	8.282%	$101.3953	$101.40	$101.40	$101.40
Purchase #2	$157.65	9.113%	$172.0166	$172.02	$172.00	$172.00
Purchase #3	$213.74	4.247%	$222.8175	$222.82	$222.80	$222.80
Purchase #4	$89.26	5.650%	$94.3032	$94.30	$94.30	$94.30
Purchase #5	$88.25	13.327%	$100.0111	$100.01	$100.00	$100.00
Purchase #6	$54.58	4.824%	$57.2129	$57.21	$57.20	$57.20
Purchase #7	$138.88	3.334%	$143.5103	$143.51	$143.50	$143.50
7 purchase totals =	$836.00		$891.2669	$891.27	$891.20	$891.20