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	$214.47	10.786%	$237.6027	$237.60	$237.60	$237.60
Purchase #2	$23.78	6.125%	$25.2365	$25.24	$25.25	$25.20
Purchase #3	$70.60	11.684%	$78.8489	$78.85	$78.85	$78.80
Purchase #4	$103.47	12.544%	$116.4493	$116.45	$116.45	$116.40
Purchase #5	$184.26	3.763%	$191.1937	$191.19	$191.20	$191.20
Purchase #6	$179.69	11.687%	$200.6904	$200.69	$200.70	$200.70
Purchase #7	$6.46	13.277%	$7.3177	$7.32	$7.30	$7.30
7 purchase totals =	$782.73		$857.3392	$857.34	$857.35	$857.20