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	$85.80	7.447%	$92.1895	$92.19	$92.20	$92.20
Purchase #2	$70.41	12.153%	$78.9669	$78.97	$78.95	$79.00
Purchase #3	$236.98	7.663%	$255.1398	$255.14	$255.15	$255.10
Purchase #4	$100.80	12.617%	$113.5179	$113.52	$113.50	$113.50
Purchase #5	$43.37	12.722%	$48.8875	$48.89	$48.90	$48.90
Purchase #6	$75.33	8.479%	$81.7172	$81.72	$81.70	$81.70
Purchase #7	$94.82	6.134%	$100.6363	$100.64	$100.65	$100.60
7 purchase totals =	$707.51		$771.0551	$771.07	$771.05	$771.00