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	$12.81	13.873%	$14.5871	$14.59	$14.60	$14.60
Purchase #2	$113.34	13.658%	$128.82	$128.82	$128.80	$128.80
Purchase #3	$84.79	4.785%	$88.8472	$88.85	$88.85	$88.80
Purchase #4	$218.42	11.622%	$243.8048	$243.80	$243.80	$243.80
Purchase #5	$207.94	7.243%	$223.0011	$223.00	$223.00	$223.00
Purchase #6	$133.73	8.602%	$145.2335	$145.23	$145.25	$145.20
Purchase #7	$160.86	6.504%	$171.3223	$171.32	$171.30	$171.30
7 purchase totals =	$931.89		$1,015.6160	$1,015.61	$1,015.60	$1,015.50