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	$218.27	8.806%	$237.4909	$237.49	$237.50	$237.50
Purchase #2	$18.89	4.403%	$19.7217	$19.72	$19.70	$19.70
Purchase #3	$91.90	7.168%	$98.4874	$98.49	$98.50	$98.50
Purchase #4	$78.80	9.665%	$86.416	$86.42	$86.40	$86.40
Purchase #5	$122.98	13.446%	$139.5159	$139.52	$139.50	$139.50
Purchase #6	$190.29	13.736%	$216.4282	$216.43	$216.45	$216.40
Purchase #7	$110.81	11.229%	$123.2529	$123.25	$123.25	$123.30
7 purchase totals =	$831.94		$921.3130	$921.32	$921.30	$921.30