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	$90.60	4.794%	$94.9434	$94.94	$94.95	$94.90
Purchase #2	$85.48	5.437%	$90.1275	$90.13	$90.15	$90.10
Purchase #3	$172.86	8.110%	$186.8789	$186.88	$186.90	$186.90
Purchase #4	$203.94	11.158%	$226.6956	$226.70	$226.70	$226.70
Purchase #5	$123.66	4.729%	$129.5079	$129.51	$129.50	$129.50
Purchase #6	$167.97	6.314%	$178.5756	$178.58	$178.60	$178.60
Purchase #7	$105.88	12.469%	$119.0822	$119.08	$119.10	$119.10
7 purchase totals =	$950.39		$1,025.8111	$1,025.82	$1,025.90	$1,025.80