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	$213.71	13.637%	$242.8536	$242.85	$242.85	$242.90
Purchase #2	$68.64	10.142%	$75.6015	$75.60	$75.60	$75.60
Purchase #3	$185.38	4.115%	$193.0084	$193.01	$193.00	$193.00
Purchase #4	$136.76	10.329%	$150.8859	$150.89	$150.90	$150.90
Purchase #5	$41.60	5.385%	$43.8402	$43.84	$43.85	$43.80
Purchase #6	$223.80	10.111%	$246.4284	$246.43	$246.45	$246.40
Purchase #7	$79.27	12.703%	$89.3397	$89.34	$89.35	$89.30
7 purchase totals =	$949.16		$1,041.9577	$1,041.96	$1,042.00	$1,041.90