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	$65.94	8.737%	$71.7012	$71.70	$71.70	$71.70
Purchase #2	$72.50	13.769%	$82.4825	$82.48	$82.50	$82.50
Purchase #3	$189.41	4.528%	$197.9865	$197.99	$198.00	$198.00
Purchase #4	$104.90	4.263%	$109.3719	$109.37	$109.35	$109.40
Purchase #5	$149.34	12.855%	$168.5377	$168.54	$168.55	$168.50
Purchase #6	$246.48	3.835%	$255.9325	$255.93	$255.95	$255.90
Purchase #7	$105.71	12.219%	$118.6267	$118.63	$118.65	$118.60
7 purchase totals =	$934.28		$1,004.6390	$1,004.64	$1,004.70	$1,004.60