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	$116.49	12.443%	$130.9849	$130.98	$131.00	$131.00
Purchase #2	$118.73	3.840%	$123.2892	$123.29	$123.30	$123.30
Purchase #3	$99.83	12.734%	$112.5424	$112.54	$112.55	$112.50
Purchase #4	$185.25	5.517%	$195.4702	$195.47	$195.45	$195.50
Purchase #5	$114.65	4.763%	$120.1108	$120.11	$120.10	$120.10
Purchase #6	$184.98	5.123%	$194.4565	$194.46	$194.45	$194.50
Purchase #7	$29.31	13.558%	$33.2838	$33.28	$33.30	$33.30
7 purchase totals =	$849.24		$910.1378	$910.13	$910.15	$910.20