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	$89.50	11.600%	$99.882	$99.88	$99.90	$99.90
Purchase #2	$46.43	10.389%	$51.2536	$51.25	$51.25	$51.30
Purchase #3	$25.68	12.447%	$28.8764	$28.88	$28.90	$28.90
Purchase #4	$58.29	12.374%	$65.5028	$65.50	$65.50	$65.50
Purchase #5	$186.44	13.136%	$210.9308	$210.93	$210.95	$210.90
Purchase #6	$98.71	4.311%	$102.9654	$102.97	$102.95	$103.00
Purchase #7	$157.84	13.256%	$178.7633	$178.76	$178.75	$178.80
7 purchase totals =	$662.89		$738.1743	$738.17	$738.20	$738.30