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	$131.25	7.495%	$141.0872	$141.09	$141.10	$141.10
Purchase #2	$50.34	6.693%	$53.7093	$53.71	$53.70	$53.70
Purchase #3	$80.28	13.225%	$90.897	$90.90	$90.90	$90.90
Purchase #4	$5.94	3.698%	$6.1597	$6.16	$6.15	$6.20
Purchase #5	$50.98	10.176%	$56.1677	$56.17	$56.15	$56.20
Purchase #6	$212.69	12.261%	$238.7679	$238.77	$238.75	$238.80
Purchase #7	$225.64	8.861%	$245.634	$245.63	$245.65	$245.60
7 purchase totals =	$757.12		$832.4228	$832.43	$832.40	$832.50