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	$67.85	7.507%	$72.9435	$72.94	$72.95	$72.90
Purchase #2	$5.74	11.176%	$6.3815	$6.38	$6.40	$6.40
Purchase #3	$108.89	9.644%	$119.3914	$119.39	$119.40	$119.40
Purchase #4	$99.66	7.535%	$107.1694	$107.17	$107.15	$107.20
Purchase #5	$125.75	11.246%	$139.8918	$139.89	$139.90	$139.90
Purchase #6	$87.55	3.270%	$90.4129	$90.41	$90.40	$90.40
Purchase #7	$7.85	4.599%	$8.211	$8.21	$8.20	$8.20
7 purchase totals =	$503.29		$544.4015	$544.39	$544.40	$544.40