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	$223.90	9.177%	$244.4473	$244.45	$244.45	$244.40
Purchase #2	$199.59	13.770%	$227.0735	$227.07	$227.05	$227.10
Purchase #3	$148.38	5.311%	$156.2605	$156.26	$156.25	$156.30
Purchase #4	$71.44	12.298%	$80.2257	$80.23	$80.25	$80.20
Purchase #5	$198.72	6.121%	$210.8837	$210.88	$210.90	$210.90
Purchase #6	$20.31	7.646%	$21.8629	$21.86	$21.85	$21.90
Purchase #7	$88.73	7.312%	$95.2179	$95.22	$95.20	$95.20
7 purchase totals =	$951.07		$1,035.9715	$1,035.97	$1,035.95	$1,036.00