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	$113.63	4.142%	$118.3366	$118.34	$118.35	$118.30
Purchase #2	$55.64	13.121%	$62.9405	$62.94	$62.95	$62.90
Purchase #3	$202.30	4.124%	$210.6429	$210.64	$210.65	$210.60
Purchase #4	$85.32	11.484%	$95.1181	$95.12	$95.10	$95.10
Purchase #5	$63.39	4.679%	$66.356	$66.36	$66.35	$66.40
Purchase #6	$187.33	4.795%	$196.3125	$196.31	$196.30	$196.30
Purchase #7	$189.82	9.654%	$208.1452	$208.15	$208.15	$208.10
7 purchase totals =	$897.43		$957.8518	$957.86	$957.85	$957.70