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	$38.37	6.744%	$40.9577	$40.96	$40.95	$41.00
Purchase #2	$162.57	13.409%	$184.369	$184.37	$184.35	$184.40
Purchase #3	$196.87	4.866%	$206.4497	$206.45	$206.45	$206.40
Purchase #4	$160.32	9.540%	$175.6145	$175.61	$175.60	$175.60
Purchase #5	$170.50	9.367%	$186.4707	$186.47	$186.45	$186.50
Purchase #6	$41.74	13.465%	$47.3603	$47.36	$47.35	$47.40
Purchase #7	$159.50	10.112%	$175.6286	$175.63	$175.65	$175.60
7 purchase totals =	$929.87		$1,016.8505	$1,016.85	$1,016.80	$1,016.90