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	$119.77	5.273%	$126.0855	$126.09	$126.10	$126.10
Purchase #2	$236.66	7.862%	$255.2662	$255.27	$255.25	$255.30
Purchase #3	$153.52	11.790%	$171.62	$171.62	$171.60	$171.60
Purchase #4	$81.56	12.514%	$91.7664	$91.77	$91.75	$91.80
Purchase #5	$39.84	6.486%	$42.424	$42.42	$42.40	$42.40
Purchase #6	$176.87	6.292%	$187.9987	$188.00	$188.00	$188.00
Purchase #7	$78.56	5.632%	$82.9845	$82.98	$83.00	$83.00
7 purchase totals =	$886.78		$958.1453	$958.15	$958.10	$958.20