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	$159.47	13.514%	$181.0208	$181.02	$181.00	$181.00
Purchase #2	$81.56	9.602%	$89.3914	$89.39	$89.40	$89.40
Purchase #3	$240.37	13.750%	$273.4209	$273.42	$273.40	$273.40
Purchase #4	$207.73	8.468%	$225.3206	$225.32	$225.30	$225.30
Purchase #5	$69.61	12.376%	$78.2249	$78.22	$78.20	$78.20
Purchase #6	$93.98	12.770%	$105.9812	$105.98	$106.00	$106.00
Purchase #7	$173.69	12.481%	$195.3682	$195.37	$195.35	$195.40
7 purchase totals =	$1,026.41		$1,148.7280	$1,148.72	$1,148.65	$1,148.70