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	$61.70	13.838%	$70.238	$70.24	$70.25	$70.20
Purchase #2	$33.78	10.643%	$37.3752	$37.38	$37.40	$37.40
Purchase #3	$10.70	3.311%	$11.0543	$11.05	$11.05	$11.10
Purchase #4	$166.98	9.228%	$182.3889	$182.39	$182.40	$182.40
Purchase #5	$249.34	5.430%	$262.8792	$262.88	$262.90	$262.90
Purchase #6	$69.46	11.788%	$77.6479	$77.65	$77.65	$77.60
Purchase #7	$64.53	11.526%	$71.9677	$71.97	$71.95	$72.00
7 purchase totals =	$656.49		$713.5512	$713.56	$713.60	$713.60