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	$89.76	10.865%	$99.5124	$99.51	$99.50	$99.50
Purchase #2	$222.83	12.317%	$250.276	$250.28	$250.30	$250.30
Purchase #3	$100.73	7.121%	$107.903	$107.90	$107.90	$107.90
Purchase #4	$145.57	11.221%	$161.9044	$161.90	$161.90	$161.90
Purchase #5	$250.71	4.241%	$261.3426	$261.34	$261.35	$261.30
Purchase #6	$58.50	7.398%	$62.8278	$62.83	$62.85	$62.80
Purchase #7	$62.77	3.510%	$64.9732	$64.97	$64.95	$65.00
7 purchase totals =	$930.87		$1,008.7394	$1,008.73	$1,008.75	$1,008.70