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	$139.37	12.215%	$156.394	$156.39	$156.40	$156.40
Purchase #2	$20.73	5.543%	$21.8791	$21.88	$21.90	$21.90
Purchase #3	$188.55	6.430%	$200.6738	$200.67	$200.65	$200.70
Purchase #4	$205.80	6.300%	$218.7654	$218.77	$218.75	$218.80
Purchase #5	$217.37	4.780%	$227.7603	$227.76	$227.75	$227.80
Purchase #6	$152.80	3.805%	$158.614	$158.61	$158.60	$158.60
Purchase #7	$179.99	6.311%	$191.3492	$191.35	$191.35	$191.30
7 purchase totals =	$1,104.61		$1,175.4358	$1,175.43	$1,175.40	$1,175.50