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	$203.90	9.834%	$223.9515	$223.95	$223.95	$224.00
Purchase #2	$104.51	4.473%	$109.1847	$109.18	$109.20	$109.20
Purchase #3	$87.82	4.593%	$91.8536	$91.85	$91.85	$91.90
Purchase #4	$224.55	7.644%	$241.7146	$241.71	$241.70	$241.70
Purchase #5	$63.40	3.351%	$65.5245	$65.52	$65.50	$65.50
Purchase #6	$93.83	3.508%	$97.1216	$97.12	$97.10	$97.10
Purchase #7	$225.68	3.456%	$233.4795	$233.48	$233.50	$233.50
7 purchase totals =	$1,003.69		$1,062.8300	$1,062.81	$1,062.80	$1,062.90