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	$176.78	11.249%	$196.666	$196.67	$196.65	$196.70
Purchase #2	$55.37	7.250%	$59.3843	$59.38	$59.40	$59.40
Purchase #3	$53.41	3.590%	$55.3274	$55.33	$55.35	$55.30
Purchase #4	$66.52	11.445%	$74.1332	$74.13	$74.15	$74.10
Purchase #5	$246.99	11.578%	$275.5865	$275.59	$275.60	$275.60
Purchase #6	$175.70	8.145%	$190.0108	$190.01	$190.00	$190.00
Purchase #7	$73.27	9.302%	$80.0856	$80.09	$80.10	$80.10
7 purchase totals =	$848.04		$931.1938	$931.20	$931.25	$931.20