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	$186.56	5.561%	$196.9346	$196.93	$196.95	$196.90
Purchase #2	$203.84	9.200%	$222.5933	$222.59	$222.60	$222.60
Purchase #3	$145.92	7.501%	$156.8655	$156.87	$156.85	$156.90
Purchase #4	$15.68	5.433%	$16.5319	$16.53	$16.55	$16.50
Purchase #5	$222.30	4.179%	$231.5899	$231.59	$231.60	$231.60
Purchase #6	$48.88	8.708%	$53.1365	$53.14	$53.15	$53.10
Purchase #7	$142.86	13.689%	$162.4161	$162.42	$162.40	$162.40
7 purchase totals =	$966.04		$1,040.0678	$1,040.07	$1,040.10	$1,040.00