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	$85.73	5.699%	$90.6158	$90.62	$90.60	$90.60
Purchase #2	$241.81	13.272%	$273.903	$273.90	$273.90	$273.90
Purchase #3	$19.48	10.517%	$21.5287	$21.53	$21.55	$21.50
Purchase #4	$13.50	5.308%	$14.2166	$14.22	$14.20	$14.20
Purchase #5	$162.32	9.628%	$177.9482	$177.95	$177.95	$177.90
Purchase #6	$191.39	7.557%	$205.8533	$205.85	$205.85	$205.90
Purchase #7	$243.64	10.550%	$269.344	$269.34	$269.35	$269.30
7 purchase totals =	$957.87		$1,053.4096	$1,053.41	$1,053.40	$1,053.30