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	$82.67	10.721%	$91.5331	$91.53	$91.55	$91.50
Purchase #2	$130.66	4.721%	$136.8285	$136.83	$136.85	$136.80
Purchase #3	$34.82	11.832%	$38.9399	$38.94	$38.95	$38.90
Purchase #4	$212.64	10.153%	$234.2293	$234.23	$234.25	$234.20
Purchase #5	$192.42	13.661%	$218.7065	$218.71	$218.70	$218.70
Purchase #6	$174.65	4.154%	$181.905	$181.91	$181.90	$181.90
Purchase #7	$113.53	5.598%	$119.8854	$119.89	$119.90	$119.90
7 purchase totals =	$941.39		$1,022.0277	$1,022.04	$1,022.10	$1,021.90