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	$72.96	7.580%	$78.4904	$78.49	$78.50	$78.50
Purchase #2	$151.38	13.626%	$172.007	$172.01	$172.00	$172.00
Purchase #3	$205.65	8.303%	$222.7251	$222.73	$222.75	$222.70
Purchase #4	$227.53	4.151%	$236.9748	$236.97	$236.95	$237.00
Purchase #5	$228.42	6.794%	$243.9389	$243.94	$243.95	$243.90
Purchase #6	$12.88	7.486%	$13.8442	$13.84	$13.85	$13.80
Purchase #7	$83.66	7.617%	$90.0324	$90.03	$90.05	$90.00
7 purchase totals =	$982.48		$1,058.0128	$1,058.01	$1,058.05	$1,057.90