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	$78.75	6.434%	$83.8168	$83.82	$83.80	$83.80
Purchase #2	$6.97	9.682%	$7.6448	$7.64	$7.65	$7.60
Purchase #3	$65.93	10.192%	$72.6496	$72.65	$72.65	$72.60
Purchase #4	$138.54	5.162%	$145.6914	$145.69	$145.70	$145.70
Purchase #5	$36.75	10.744%	$40.6984	$40.70	$40.70	$40.70
Purchase #6	$140.64	11.567%	$156.9078	$156.91	$156.90	$156.90
Purchase #7	$171.65	4.818%	$179.9201	$179.92	$179.90	$179.90
7 purchase totals =	$639.23		$687.3289	$687.33	$687.30	$687.20