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	$166.36	13.284%	$188.4593	$188.46	$188.45	$188.50
Purchase #2	$169.62	3.802%	$176.069	$176.07	$176.05	$176.10
Purchase #3	$76.90	10.550%	$85.013	$85.01	$85.00	$85.00
Purchase #4	$246.61	13.426%	$279.7199	$279.72	$279.70	$279.70
Purchase #5	$190.51	10.231%	$210.0011	$210.00	$210.00	$210.00
Purchase #6	$19.75	5.772%	$20.89	$20.89	$20.90	$20.90
Purchase #7	$97.27	3.160%	$100.3437	$100.34	$100.35	$100.30
7 purchase totals =	$967.02		$1,060.4960	$1,060.49	$1,060.45	$1,060.50