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	$89.89	5.870%	$95.1665	$95.17	$95.15	$95.20
Purchase #2	$21.76	5.238%	$22.8998	$22.90	$22.90	$22.90
Purchase #3	$141.32	13.636%	$160.5904	$160.59	$160.60	$160.60
Purchase #4	$216.42	11.248%	$240.7629	$240.76	$240.75	$240.80
Purchase #5	$214.94	3.385%	$222.2157	$222.22	$222.20	$222.20
Purchase #6	$238.25	5.307%	$250.8939	$250.89	$250.90	$250.90
Purchase #7	$87.85	3.709%	$91.1084	$91.11	$91.10	$91.10
7 purchase totals =	$1,010.43		$1,083.6376	$1,083.64	$1,083.60	$1,083.70