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	$53.33	12.641%	$60.0714	$60.07	$60.05	$60.10
Purchase #2	$76.36	7.240%	$81.8885	$81.89	$81.90	$81.90
Purchase #3	$160.81	6.222%	$170.8156	$170.82	$170.80	$170.80
Purchase #4	$95.94	9.571%	$105.1224	$105.12	$105.10	$105.10
Purchase #5	$168.77	10.716%	$186.8554	$186.86	$186.85	$186.90
Purchase #6	$159.81	6.312%	$169.8972	$169.90	$169.90	$169.90
Purchase #7	$50.57	10.420%	$55.8394	$55.84	$55.85	$55.80
7 purchase totals =	$765.59		$830.4899	$830.50	$830.45	$830.50