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	$14.90	9.205%	$16.2715	$16.27	$16.25	$16.30
Purchase #2	$221.33	9.229%	$241.7565	$241.76	$241.75	$241.80
Purchase #3	$111.58	6.810%	$119.1786	$119.18	$119.20	$119.20
Purchase #4	$71.84	13.465%	$81.5133	$81.51	$81.50	$81.50
Purchase #5	$67.87	7.212%	$72.7648	$72.76	$72.75	$72.80
Purchase #6	$55.69	6.354%	$59.2285	$59.23	$59.25	$59.20
Purchase #7	$31.39	10.520%	$34.6922	$34.69	$34.70	$34.70
7 purchase totals =	$574.60		$625.4054	$625.40	$625.40	$625.50