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	$141.32	4.137%	$147.1664	$147.17	$147.15	$147.20
Purchase #2	$23.35	9.623%	$25.597	$25.60	$25.60	$25.60
Purchase #3	$25.84	10.140%	$28.4602	$28.46	$28.45	$28.50
Purchase #4	$215.63	7.546%	$231.9014	$231.90	$231.90	$231.90
Purchase #5	$15.56	10.268%	$17.1577	$17.16	$17.15	$17.20
Purchase #6	$107.94	7.674%	$116.2233	$116.22	$116.20	$116.20
Purchase #7	$78.90	13.427%	$89.4939	$89.49	$89.50	$89.50
7 purchase totals =	$608.54		$655.9999	$656.00	$655.95	$656.10