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	$45.49	6.189%	$48.3054	$48.31	$48.30	$48.30
Purchase #2	$53.34	12.222%	$59.8592	$59.86	$59.85	$59.90
Purchase #3	$201.68	4.501%	$210.7576	$210.76	$210.75	$210.80
Purchase #4	$116.66	7.581%	$125.504	$125.50	$125.50	$125.50
Purchase #5	$81.84	5.803%	$86.5892	$86.59	$86.60	$86.60
Purchase #6	$243.30	12.553%	$273.8414	$273.84	$273.85	$273.80
Purchase #7	$127.97	9.113%	$139.6319	$139.63	$139.65	$139.60
7 purchase totals =	$870.28		$944.4887	$944.49	$944.50	$944.50