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	$175.40	13.292%	$198.7142	$198.71	$198.70	$198.70
Purchase #2	$151.75	10.281%	$167.3514	$167.35	$167.35	$167.40
Purchase #3	$172.52	11.339%	$192.082	$192.08	$192.10	$192.10
Purchase #4	$177.39	5.773%	$187.6307	$187.63	$187.65	$187.60
Purchase #5	$205.94	13.375%	$233.4845	$233.48	$233.50	$233.50
Purchase #6	$52.27	13.458%	$59.3045	$59.30	$59.30	$59.30
Purchase #7	$223.94	4.746%	$234.5682	$234.57	$234.55	$234.60
7 purchase totals =	$1,159.21		$1,273.1355	$1,273.12	$1,273.15	$1,273.20