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	$102.43	13.647%	$116.4086	$116.41	$116.40	$116.40
Purchase #2	$242.54	11.423%	$270.2453	$270.25	$270.25	$270.20
Purchase #3	$39.97	7.811%	$43.0921	$43.09	$43.10	$43.10
Purchase #4	$104.93	10.429%	$115.8731	$115.87	$115.85	$115.90
Purchase #5	$249.38	10.316%	$275.106	$275.11	$275.10	$275.10
Purchase #6	$97.33	11.583%	$108.6037	$108.60	$108.60	$108.60
Purchase #7	$95.88	10.488%	$105.9359	$105.94	$105.95	$105.90
7 purchase totals =	$932.46		$1,035.2647	$1,035.27	$1,035.25	$1,035.20