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	$187.34	8.672%	$203.5861	$203.59	$203.60	$203.60
Purchase #2	$232.56	4.862%	$243.8671	$243.87	$243.85	$243.90
Purchase #3	$197.45	8.434%	$214.1029	$214.10	$214.10	$214.10
Purchase #4	$142.66	11.133%	$158.5423	$158.54	$158.55	$158.50
Purchase #5	$124.72	12.320%	$140.0855	$140.09	$140.10	$140.10
Purchase #6	$55.32	7.471%	$59.453	$59.45	$59.45	$59.50
Purchase #7	$88.81	4.279%	$92.6102	$92.61	$92.60	$92.60
7 purchase totals =	$1,028.86		$1,112.2471	$1,112.25	$1,112.25	$1,112.30