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	$118.64	11.115%	$131.8268	$131.83	$131.85	$131.80
Purchase #2	$244.72	12.383%	$275.0237	$275.02	$275.00	$275.00
Purchase #3	$215.97	4.455%	$225.5915	$225.59	$225.60	$225.60
Purchase #4	$127.56	11.359%	$142.0495	$142.05	$142.05	$142.00
Purchase #5	$94.57	8.107%	$102.2368	$102.24	$102.25	$102.20
Purchase #6	$241.78	10.680%	$267.6021	$267.60	$267.60	$267.60
Purchase #7	$16.30	10.695%	$18.0433	$18.04	$18.05	$18.00
7 purchase totals =	$1,059.54		$1,162.3737	$1,162.37	$1,162.40	$1,162.20