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	$141.25	10.747%	$156.4301	$156.43	$156.45	$156.40
Purchase #2	$155.51	9.297%	$169.9678	$169.97	$169.95	$170.00
Purchase #3	$243.37	4.706%	$254.823	$254.82	$254.80	$254.80
Purchase #4	$95.51	10.294%	$105.3418	$105.34	$105.35	$105.30
Purchase #5	$77.97	7.280%	$83.6462	$83.65	$83.65	$83.60
Purchase #6	$157.61	9.502%	$172.5861	$172.59	$172.60	$172.60
Purchase #7	$101.82	8.760%	$110.7394	$110.74	$110.75	$110.70
7 purchase totals =	$973.04		$1,053.5344	$1,053.54	$1,053.55	$1,053.40