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	$198.52	13.640%	$225.5981	$225.60	$225.60	$225.60
Purchase #2	$81.75	12.863%	$92.2655	$92.27	$92.25	$92.30
Purchase #3	$198.79	7.109%	$212.922	$212.92	$212.90	$212.90
Purchase #4	$115.55	13.452%	$131.0938	$131.09	$131.10	$131.10
Purchase #5	$78.51	10.667%	$86.8847	$86.88	$86.90	$86.90
Purchase #6	$172.46	4.521%	$180.2569	$180.26	$180.25	$180.30
Purchase #7	$108.31	3.427%	$112.0218	$112.02	$112.00	$112.00
7 purchase totals =	$953.89		$1,041.0428	$1,041.04	$1,041.00	$1,041.10