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	$114.83	11.115%	$127.5934	$127.59	$127.60	$127.60
Purchase #2	$7.96	10.544%	$8.7993	$8.80	$8.80	$8.80
Purchase #3	$220.38	10.735%	$244.0378	$244.04	$244.05	$244.00
Purchase #4	$231.42	9.290%	$252.9189	$252.92	$252.90	$252.90
Purchase #5	$174.35	6.857%	$186.3052	$186.31	$186.30	$186.30
Purchase #6	$52.34	7.533%	$56.2828	$56.28	$56.30	$56.30
Purchase #7	$99.61	5.700%	$105.2878	$105.29	$105.30	$105.30
7 purchase totals =	$900.89		$981.2252	$981.23	$981.25	$981.20