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	7.134%	$212.6824	$212.68	$212.70	$212.70
Purchase #2	$218.54	9.523%	$239.3516	$239.35	$239.35	$239.40
Purchase #3	$220.93	4.828%	$231.5965	$231.60	$231.60	$231.60
Purchase #4	$151.90	13.263%	$172.0465	$172.05	$172.05	$172.00
Purchase #5	$210.73	3.635%	$218.39	$218.39	$218.40	$218.40
Purchase #6	$119.76	5.123%	$125.8953	$125.90	$125.90	$125.90
Purchase #7	$88.60	13.196%	$100.2917	$100.29	$100.30	$100.30
7 purchase totals =	$1,208.98		$1,300.2540	$1,300.26	$1,300.30	$1,300.30