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	$198.38	8.534%	$215.3097	$215.31	$215.30	$215.30
Purchase #2	$201.68	4.440%	$210.6346	$210.63	$210.65	$210.60
Purchase #3	$82.62	8.264%	$89.4477	$89.45	$89.45	$89.40
Purchase #4	$114.81	11.373%	$127.8673	$127.87	$127.85	$127.90
Purchase #5	$183.34	7.385%	$196.8797	$196.88	$196.90	$196.90
Purchase #6	$249.28	5.290%	$262.4669	$262.47	$262.45	$262.50
Purchase #7	$221.89	11.221%	$246.7883	$246.79	$246.80	$246.80
7 purchase totals =	$1,252.00		$1,349.3942	$1,349.40	$1,349.40	$1,349.40