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	$197.81	12.241%	$222.0239	$222.02	$222.00	$222.00
Purchase #2	$19.77	5.601%	$20.8773	$20.88	$20.90	$20.90
Purchase #3	$61.74	13.183%	$69.8792	$69.88	$69.90	$69.90
Purchase #4	$90.64	10.415%	$100.0802	$100.08	$100.10	$100.10
Purchase #5	$68.62	13.738%	$78.047	$78.05	$78.05	$78.00
Purchase #6	$197.51	6.597%	$210.5397	$210.54	$210.55	$210.50
Purchase #7	$203.35	11.849%	$227.4449	$227.44	$227.45	$227.40
7 purchase totals =	$839.44		$928.8922	$928.89	$928.95	$928.80