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	$200.78	9.872%	$220.601	$220.60	$220.60	$220.60
Purchase #2	$189.87	10.703%	$210.1918	$210.19	$210.20	$210.20
Purchase #3	$198.86	13.331%	$225.37	$225.37	$225.35	$225.40
Purchase #4	$156.54	5.647%	$165.3798	$165.38	$165.40	$165.40
Purchase #5	$61.86	5.295%	$65.1355	$65.14	$65.15	$65.10
Purchase #6	$100.51	12.770%	$113.3451	$113.35	$113.35	$113.30
Purchase #7	$98.77	6.486%	$105.1762	$105.18	$105.20	$105.20
7 purchase totals =	$1,007.19		$1,105.1994	$1,105.21	$1,105.25	$1,105.20