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	$142.69	10.487%	$157.6539	$157.65	$157.65	$157.70
Purchase #2	$215.98	7.841%	$232.915	$232.92	$232.90	$232.90
Purchase #3	$203.90	9.625%	$223.5254	$223.53	$223.55	$223.50
Purchase #4	$59.32	11.472%	$66.1252	$66.13	$66.15	$66.10
Purchase #5	$112.72	13.168%	$127.563	$127.56	$127.55	$127.60
Purchase #6	$40.92	7.214%	$43.872	$43.87	$43.85	$43.90
Purchase #7	$95.94	5.414%	$101.1342	$101.13	$101.15	$101.10
7 purchase totals =	$871.47		$952.7887	$952.79	$952.80	$952.80