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	$79.28	11.789%	$88.6263	$88.63	$88.65	$88.60
Purchase #2	$213.60	6.711%	$227.9347	$227.93	$227.95	$227.90
Purchase #3	$31.93	3.278%	$32.9767	$32.98	$33.00	$33.00
Purchase #4	$77.38	12.283%	$86.8846	$86.88	$86.90	$86.90
Purchase #5	$201.33	11.534%	$224.5514	$224.55	$224.55	$224.60
Purchase #6	$143.45	6.396%	$152.6251	$152.63	$152.65	$152.60
Purchase #7	$118.94	10.515%	$131.4465	$131.45	$131.45	$131.40
7 purchase totals =	$865.91		$945.0453	$945.05	$945.15	$945.00