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	$185.73	13.135%	$210.1256	$210.13	$210.15	$210.10
Purchase #2	$196.88	6.148%	$208.9842	$208.98	$209.00	$209.00
Purchase #3	$117.53	8.497%	$127.5165	$127.52	$127.50	$127.50
Purchase #4	$158.96	11.112%	$176.6236	$176.62	$176.60	$176.60
Purchase #5	$164.37	11.602%	$183.4402	$183.44	$183.45	$183.40
Purchase #6	$5.88	10.801%	$6.5151	$6.52	$6.50	$6.50
Purchase #7	$30.68	3.688%	$31.8115	$31.81	$31.80	$31.80
7 purchase totals =	$860.03		$945.0167	$945.02	$945.00	$944.90