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	$64.82	10.317%	$71.5075	$71.51	$71.50	$71.50
Purchase #2	$151.50	13.198%	$171.495	$171.50	$171.50	$171.50
Purchase #3	$182.32	9.602%	$199.8264	$199.83	$199.85	$199.80
Purchase #4	$190.37	12.104%	$213.4124	$213.41	$213.40	$213.40
Purchase #5	$199.51	5.484%	$210.4511	$210.45	$210.45	$210.50
Purchase #6	$59.49	8.755%	$64.6983	$64.70	$64.70	$64.70
Purchase #7	$81.39	5.281%	$85.6882	$85.69	$85.70	$85.70
7 purchase totals =	$929.40		$1,017.0789	$1,017.09	$1,017.10	$1,017.10