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	$85.65	3.710%	$88.8276	$88.83	$88.85	$88.80
Purchase #2	$133.78	12.138%	$150.0182	$150.02	$150.00	$150.00
Purchase #3	$148.90	10.793%	$164.9708	$164.97	$164.95	$165.00
Purchase #4	$230.73	9.673%	$253.0485	$253.05	$253.05	$253.00
Purchase #5	$86.58	4.617%	$90.5774	$90.58	$90.60	$90.60
Purchase #6	$95.59	3.152%	$98.603	$98.60	$98.60	$98.60
Purchase #7	$185.73	7.427%	$199.5242	$199.52	$199.50	$199.50
7 purchase totals =	$966.96		$1,045.5697	$1,045.57	$1,045.55	$1,045.50