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	$106.94	4.245%	$111.4796	$111.48	$111.50	$111.50
Purchase #2	$173.69	7.238%	$186.2617	$186.26	$186.25	$186.30
Purchase #3	$32.25	13.304%	$36.5405	$36.54	$36.55	$36.50
Purchase #4	$160.44	4.853%	$168.2262	$168.23	$168.25	$168.20
Purchase #5	$95.67	6.801%	$102.1765	$102.18	$102.20	$102.20
Purchase #6	$99.29	9.252%	$108.4763	$108.48	$108.50	$108.50
Purchase #7	$86.53	12.701%	$97.5202	$97.52	$97.50	$97.50
7 purchase totals =	$754.81		$810.6810	$810.69	$810.75	$810.70