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	$167.85	11.266%	$186.76	$186.76	$186.75	$186.80
Purchase #2	$85.39	8.775%	$92.883	$92.88	$92.90	$92.90
Purchase #3	$228.25	10.587%	$252.4148	$252.41	$252.40	$252.40
Purchase #4	$214.57	9.393%	$234.7246	$234.72	$234.70	$234.70
Purchase #5	$84.63	5.666%	$89.4251	$89.43	$89.45	$89.40
Purchase #6	$64.93	5.575%	$68.5498	$68.55	$68.55	$68.50
Purchase #7	$165.65	12.796%	$186.8466	$186.85	$186.85	$186.80
7 purchase totals =	$1,011.27		$1,111.6039	$1,111.60	$1,111.60	$1,111.50