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	$198.42	8.424%	$215.1349	$215.13	$215.15	$215.10
Purchase #2	$42.76	8.465%	$46.3796	$46.38	$46.40	$46.40
Purchase #3	$134.29	6.230%	$142.6563	$142.66	$142.65	$142.70
Purchase #4	$228.59	11.574%	$255.047	$255.05	$255.05	$255.00
Purchase #5	$220.42	11.220%	$245.1511	$245.15	$245.15	$245.20
Purchase #6	$245.52	7.123%	$263.0084	$263.01	$263.00	$263.00
Purchase #7	$65.62	10.650%	$72.6085	$72.61	$72.60	$72.60
7 purchase totals =	$1,135.62		$1,239.9858	$1,239.99	$1,240.00	$1,240.00