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	$67.42	3.152%	$69.5451	$69.55	$69.55	$69.50
Purchase #2	$102.55	7.109%	$109.8403	$109.84	$109.85	$109.80
Purchase #3	$90.99	10.576%	$100.6131	$100.61	$100.60	$100.60
Purchase #4	$64.55	13.692%	$73.3882	$73.39	$73.40	$73.40
Purchase #5	$14.87	5.247%	$15.6502	$15.65	$15.65	$15.70
Purchase #6	$231.54	9.595%	$253.7563	$253.76	$253.75	$253.80
Purchase #7	$31.90	13.258%	$36.1293	$36.13	$36.15	$36.10
7 purchase totals =	$603.82		$658.9225	$658.93	$658.95	$658.90