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	$119.77	9.349%	$130.9673	$130.97	$130.95	$131.00
Purchase #2	$241.56	10.376%	$266.6243	$266.62	$266.60	$266.60
Purchase #3	$163.90	5.483%	$172.8866	$172.89	$172.90	$172.90
Purchase #4	$173.54	3.590%	$179.7701	$179.77	$179.75	$179.80
Purchase #5	$149.58	7.550%	$160.8733	$160.87	$160.85	$160.90
Purchase #6	$136.87	11.559%	$152.6908	$152.69	$152.70	$152.70
Purchase #7	$186.53	5.374%	$196.5541	$196.55	$196.55	$196.60
7 purchase totals =	$1,171.75		$1,260.3665	$1,260.36	$1,260.30	$1,260.50