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	$195.64	3.147%	$201.7968	$201.80	$201.80	$201.80
Purchase #2	$49.77	3.620%	$51.5717	$51.57	$51.55	$51.60
Purchase #3	$210.26	5.383%	$221.5783	$221.58	$221.60	$221.60
Purchase #4	$134.55	7.200%	$144.2376	$144.24	$144.25	$144.20
Purchase #5	$218.61	4.117%	$227.6102	$227.61	$227.60	$227.60
Purchase #6	$53.60	11.685%	$59.8632	$59.86	$59.85	$59.90
Purchase #7	$115.25	10.393%	$127.2279	$127.23	$127.25	$127.20
7 purchase totals =	$977.68		$1,033.8857	$1,033.89	$1,033.90	$1,033.90