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	$234.83	12.627%	$264.482	$264.48	$264.50	$264.50
Purchase #2	$60.76	11.687%	$67.861	$67.86	$67.85	$67.90
Purchase #3	$245.90	11.544%	$274.2867	$274.29	$274.30	$274.30
Purchase #4	$89.82	3.458%	$92.926	$92.93	$92.95	$92.90
Purchase #5	$88.52	7.848%	$95.467	$95.47	$95.45	$95.50
Purchase #6	$97.86	11.523%	$109.1364	$109.14	$109.15	$109.10
Purchase #7	$94.74	8.690%	$102.9729	$102.97	$102.95	$103.00
7 purchase totals =	$912.43		$1,007.1320	$1,007.14	$1,007.15	$1,007.20