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	$138.53	7.420%	$148.8089	$148.81	$148.80	$148.80
Purchase #2	$209.33	11.501%	$233.405	$233.41	$233.40	$233.40
Purchase #3	$198.48	5.463%	$209.323	$209.32	$209.30	$209.30
Purchase #4	$118.27	8.474%	$128.2922	$128.29	$128.30	$128.30
Purchase #5	$177.80	10.533%	$196.5277	$196.53	$196.55	$196.50
Purchase #6	$102.78	3.680%	$106.5623	$106.56	$106.55	$106.60
Purchase #7	$105.38	10.524%	$116.4702	$116.47	$116.45	$116.50
7 purchase totals =	$1,050.57		$1,139.3893	$1,139.39	$1,139.35	$1,139.40