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	$147.26	12.166%	$165.1757	$165.18	$165.20	$165.20
Purchase #2	$21.78	13.154%	$24.6449	$24.64	$24.65	$24.60
Purchase #3	$73.81	12.364%	$82.9359	$82.94	$82.95	$82.90
Purchase #4	$43.25	7.358%	$46.4323	$46.43	$46.45	$46.40
Purchase #5	$58.29	7.455%	$62.6355	$62.64	$62.65	$62.60
Purchase #6	$41.85	3.874%	$43.4713	$43.47	$43.45	$43.50
Purchase #7	$195.69	7.182%	$209.7445	$209.74	$209.75	$209.70
7 purchase totals =	$581.93		$635.0401	$635.04	$635.10	$634.90