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	$30.35	5.689%	$32.0766	$32.08	$32.10	$32.10
Purchase #2	$124.42	5.797%	$131.6326	$131.63	$131.65	$131.60
Purchase #3	$224.86	7.112%	$240.852	$240.85	$240.85	$240.90
Purchase #4	$177.87	11.361%	$198.0778	$198.08	$198.10	$198.10
Purchase #5	$160.25	4.713%	$167.8026	$167.80	$167.80	$167.80
Purchase #6	$34.74	8.533%	$37.7044	$37.70	$37.70	$37.70
Purchase #7	$194.52	7.250%	$208.6227	$208.62	$208.60	$208.60
7 purchase totals =	$947.01		$1,016.7687	$1,016.76	$1,016.80	$1,016.80