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	$38.91	13.436%	$44.1379	$44.14	$44.15	$44.10
Purchase #2	$35.56	5.597%	$37.5503	$37.55	$37.55	$37.60
Purchase #3	$125.87	9.131%	$137.3632	$137.36	$137.35	$137.40
Purchase #4	$181.26	10.275%	$199.8845	$199.88	$199.90	$199.90
Purchase #5	$137.38	10.307%	$151.5398	$151.54	$151.55	$151.50
Purchase #6	$72.79	12.819%	$82.121	$82.12	$82.10	$82.10
Purchase #7	$38.74	3.658%	$40.1571	$40.16	$40.15	$40.20
7 purchase totals =	$630.51		$692.7538	$692.75	$692.75	$692.80