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	$154.89	12.439%	$174.1568	$174.16	$174.15	$174.20
Purchase #2	$19.72	8.589%	$21.4138	$21.41	$21.40	$21.40
Purchase #3	$77.88	10.193%	$85.8183	$85.82	$85.80	$85.80
Purchase #4	$198.29	9.110%	$216.3542	$216.35	$216.35	$216.40
Purchase #5	$17.38	4.602%	$18.1798	$18.18	$18.20	$18.20
Purchase #6	$164.44	13.586%	$186.7808	$186.78	$186.80	$186.80
Purchase #7	$20.67	10.754%	$22.8929	$22.89	$22.90	$22.90
7 purchase totals =	$653.27		$725.5966	$725.59	$725.60	$725.70