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	$118.62	6.700%	$126.5675	$126.57	$126.55	$126.60
Purchase #2	$78.53	10.252%	$86.5809	$86.58	$86.60	$86.60
Purchase #3	$184.83	6.291%	$196.4577	$196.46	$196.45	$196.50
Purchase #4	$17.88	7.836%	$19.2811	$19.28	$19.30	$19.30
Purchase #5	$121.54	8.426%	$131.781	$131.78	$131.80	$131.80
Purchase #6	$8.27	8.516%	$8.9743	$8.97	$8.95	$9.00
Purchase #7	$111.67	10.689%	$123.6064	$123.61	$123.60	$123.60
7 purchase totals =	$641.34		$693.2489	$693.25	$693.25	$693.40