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	$12.91	4.780%	$13.5271	$13.53	$13.55	$13.50
Purchase #2	$150.82	11.140%	$167.6213	$167.62	$167.60	$167.60
Purchase #3	$145.28	13.802%	$165.3315	$165.33	$165.35	$165.30
Purchase #4	$215.77	7.449%	$231.8427	$231.84	$231.85	$231.80
Purchase #5	$56.38	4.814%	$59.0941	$59.09	$59.10	$59.10
Purchase #6	$230.70	5.739%	$243.9399	$243.94	$243.95	$243.90
Purchase #7	$13.92	13.233%	$15.762	$15.76	$15.75	$15.80
7 purchase totals =	$825.78		$897.1186	$897.11	$897.15	$897.00