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	$41.56	7.756%	$44.7834	$44.78	$44.80	$44.80
Purchase #2	$176.49	11.191%	$196.241	$196.24	$196.25	$196.20
Purchase #3	$131.90	4.223%	$137.4701	$137.47	$137.45	$137.50
Purchase #4	$109.37	4.784%	$114.6023	$114.60	$114.60	$114.60
Purchase #5	$153.48	9.263%	$167.6969	$167.70	$167.70	$167.70
Purchase #6	$153.86	9.313%	$168.189	$168.19	$168.20	$168.20
Purchase #7	$167.49	11.264%	$186.3561	$186.36	$186.35	$186.40
7 purchase totals =	$934.15		$1,015.3388	$1,015.34	$1,015.35	$1,015.40