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	$91.57	11.147%	$101.7773	$101.78	$101.80	$101.80
Purchase #2	$26.51	8.223%	$28.6899	$28.69	$28.70	$28.70
Purchase #3	$96.84	7.284%	$103.8938	$103.89	$103.90	$103.90
Purchase #4	$181.68	4.815%	$190.4279	$190.43	$190.45	$190.40
Purchase #5	$28.25	13.627%	$32.0996	$32.10	$32.10	$32.10
Purchase #6	$31.88	3.347%	$32.947	$32.95	$32.95	$32.90
Purchase #7	$168.68	9.644%	$184.9475	$184.95	$184.95	$184.90
7 purchase totals =	$625.41		$674.7830	$674.79	$674.85	$674.70