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	$207.82	3.696%	$215.501	$215.50	$215.50	$215.50
Purchase #2	$119.57	9.804%	$131.2926	$131.29	$131.30	$131.30
Purchase #3	$68.40	5.500%	$72.162	$72.16	$72.15	$72.20
Purchase #4	$158.96	3.854%	$165.0863	$165.09	$165.10	$165.10
Purchase #5	$63.85	11.368%	$71.1085	$71.11	$71.10	$71.10
Purchase #6	$31.53	4.618%	$32.9861	$32.99	$33.00	$33.00
Purchase #7	$235.61	10.462%	$260.2595	$260.26	$260.25	$260.30
7 purchase totals =	$885.74		$948.3960	$948.40	$948.40	$948.50