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	$120.89	13.547%	$137.267	$137.27	$137.25	$137.30
Purchase #2	$67.51	13.322%	$76.5037	$76.50	$76.50	$76.50
Purchase #3	$37.35	3.483%	$38.6509	$38.65	$38.65	$38.70
Purchase #4	$78.50	6.327%	$83.4667	$83.47	$83.45	$83.50
Purchase #5	$210.36	6.684%	$224.4205	$224.42	$224.40	$224.40
Purchase #6	$110.88	5.768%	$117.2756	$117.28	$117.30	$117.30
Purchase #7	$85.34	3.370%	$88.216	$88.22	$88.20	$88.20
7 purchase totals =	$710.83		$765.8004	$765.81	$765.75	$765.90