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	$233.32	8.683%	$253.5792	$253.58	$253.60	$253.60
Purchase #2	$12.40	11.671%	$13.8472	$13.85	$13.85	$13.80
Purchase #3	$73.39	8.146%	$79.3683	$79.37	$79.35	$79.40
Purchase #4	$156.91	6.329%	$166.8408	$166.84	$166.85	$166.80
Purchase #5	$151.95	10.166%	$167.3972	$167.40	$167.40	$167.40
Purchase #6	$131.72	8.766%	$143.2666	$143.27	$143.25	$143.30
Purchase #7	$177.75	10.539%	$196.4831	$196.48	$196.50	$196.50
7 purchase totals =	$937.44		$1,020.7824	$1,020.79	$1,020.80	$1,020.80