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	$234.67	12.436%	$263.8536	$263.85	$263.85	$263.90
Purchase #2	$25.54	10.352%	$28.1839	$28.18	$28.20	$28.20
Purchase #3	$171.91	7.400%	$184.6313	$184.63	$184.65	$184.60
Purchase #4	$39.45	12.685%	$44.4542	$44.45	$44.45	$44.50
Purchase #5	$75.33	4.768%	$78.9217	$78.92	$78.90	$78.90
Purchase #6	$88.61	12.761%	$99.9175	$99.92	$99.90	$99.90
Purchase #7	$224.93	3.513%	$232.8318	$232.83	$232.85	$232.80
7 purchase totals =	$860.44		$932.7940	$932.78	$932.80	$932.80