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	$68.39	13.450%	$77.5885	$77.59	$77.60	$77.60
Purchase #2	$158.31	13.615%	$179.8639	$179.86	$179.85	$179.90
Purchase #3	$196.47	12.404%	$220.8401	$220.84	$220.85	$220.80
Purchase #4	$205.96	12.308%	$231.3096	$231.31	$231.30	$231.30
Purchase #5	$70.95	13.614%	$80.6091	$80.61	$80.60	$80.60
Purchase #6	$198.27	10.157%	$218.4083	$218.41	$218.40	$218.40
Purchase #7	$77.28	5.633%	$81.6332	$81.63	$81.65	$81.60
7 purchase totals =	$975.63		$1,090.2527	$1,090.25	$1,090.25	$1,090.20