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	$68.69	5.871%	$72.7228	$72.72	$72.70	$72.70
Purchase #2	$48.65	5.596%	$51.3725	$51.37	$51.35	$51.40
Purchase #3	$74.78	12.165%	$83.877	$83.88	$83.90	$83.90
Purchase #4	$157.70	9.398%	$172.5206	$172.52	$172.50	$172.50
Purchase #5	$135.62	5.550%	$143.1469	$143.15	$143.15	$143.10
Purchase #6	$63.85	12.612%	$71.9028	$71.90	$71.90	$71.90
Purchase #7	$220.55	6.838%	$235.6312	$235.63	$235.65	$235.60
7 purchase totals =	$769.84		$831.1738	$831.17	$831.15	$831.10