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	$71.80	6.557%	$76.5079	$76.51	$76.50	$76.50
Purchase #2	$100.27	11.222%	$111.5223	$111.52	$111.50	$111.50
Purchase #3	$95.52	7.364%	$102.5541	$102.55	$102.55	$102.60
Purchase #4	$240.91	13.329%	$273.0209	$273.02	$273.00	$273.00
Purchase #5	$234.41	6.240%	$249.0372	$249.04	$249.05	$249.00
Purchase #6	$227.39	6.769%	$242.782	$242.78	$242.80	$242.80
Purchase #7	$7.57	8.179%	$8.1892	$8.19	$8.20	$8.20
7 purchase totals =	$977.87		$1,063.6136	$1,063.61	$1,063.60	$1,063.60