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	$222.89	6.687%	$237.7947	$237.79	$237.80	$237.80
Purchase #2	$160.25	4.792%	$167.9292	$167.93	$167.95	$167.90
Purchase #3	$245.56	10.215%	$270.644	$270.64	$270.65	$270.60
Purchase #4	$27.66	8.270%	$29.9475	$29.95	$29.95	$29.90
Purchase #5	$169.73	13.540%	$192.7114	$192.71	$192.70	$192.70
Purchase #6	$71.71	8.788%	$78.0119	$78.01	$78.00	$78.00
Purchase #7	$81.55	6.563%	$86.9021	$86.90	$86.90	$86.90
7 purchase totals =	$979.35		$1,063.9408	$1,063.93	$1,063.95	$1,063.80