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	$105.81	6.714%	$112.9141	$112.91	$112.90	$112.90
Purchase #2	$214.85	7.599%	$231.1765	$231.18	$231.20	$231.20
Purchase #3	$38.57	4.610%	$40.3481	$40.35	$40.35	$40.30
Purchase #4	$166.38	12.170%	$186.6284	$186.63	$186.65	$186.60
Purchase #5	$226.82	11.711%	$253.3829	$253.38	$253.40	$253.40
Purchase #6	$122.55	11.445%	$136.5758	$136.58	$136.60	$136.60
Purchase #7	$149.89	11.623%	$167.3117	$167.31	$167.30	$167.30
7 purchase totals =	$1,024.87		$1,128.3375	$1,128.34	$1,128.40	$1,128.30