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	$40.73	13.466%	$46.2147	$46.21	$46.20	$46.20
Purchase #2	$187.71	5.746%	$198.4958	$198.50	$198.50	$198.50
Purchase #3	$218.82	6.665%	$233.4044	$233.40	$233.40	$233.40
Purchase #4	$85.40	5.140%	$89.7896	$89.79	$89.80	$89.80
Purchase #5	$12.81	12.560%	$14.4189	$14.42	$14.40	$14.40
Purchase #6	$135.68	4.251%	$141.4478	$141.45	$141.45	$141.40
Purchase #7	$25.91	13.362%	$29.3721	$29.37	$29.35	$29.40
7 purchase totals =	$707.06		$753.1433	$753.14	$753.10	$753.10