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	$168.95	11.786%	$188.8624	$188.86	$188.85	$188.90
Purchase #2	$139.81	12.238%	$156.9199	$156.92	$156.90	$156.90
Purchase #3	$163.33	5.786%	$172.7803	$172.78	$172.80	$172.80
Purchase #4	$224.56	8.641%	$243.9642	$243.96	$243.95	$244.00
Purchase #5	$182.65	10.550%	$201.9196	$201.92	$201.90	$201.90
Purchase #6	$182.93	3.240%	$188.8569	$188.86	$188.85	$188.90
Purchase #7	$78.82	3.476%	$81.5598	$81.56	$81.55	$81.60
7 purchase totals =	$1,141.05		$1,234.8631	$1,234.86	$1,234.80	$1,235.00