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	$106.81	9.611%	$117.0755	$117.08	$117.10	$117.10
Purchase #2	$249.26	12.805%	$281.1777	$281.18	$281.20	$281.20
Purchase #3	$38.84	12.260%	$43.6018	$43.60	$43.60	$43.60
Purchase #4	$74.31	11.482%	$82.8423	$82.84	$82.85	$82.80
Purchase #5	$234.27	5.815%	$247.8928	$247.89	$247.90	$247.90
Purchase #6	$174.60	7.409%	$187.5361	$187.54	$187.55	$187.50
Purchase #7	$39.47	3.640%	$40.9067	$40.91	$40.90	$40.90
7 purchase totals =	$917.56		$1,001.0329	$1,001.04	$1,001.10	$1,001.00