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	$44.25	5.111%	$46.5116	$46.51	$46.50	$46.50
Purchase #2	$12.52	9.156%	$13.6663	$13.67	$13.65	$13.70
Purchase #3	$42.37	3.326%	$43.7792	$43.78	$43.80	$43.80
Purchase #4	$133.70	11.520%	$149.1022	$149.10	$149.10	$149.10
Purchase #5	$25.89	8.392%	$28.0627	$28.06	$28.05	$28.10
Purchase #6	$205.60	6.192%	$218.3308	$218.33	$218.35	$218.30
Purchase #7	$29.85	11.836%	$33.383	$33.38	$33.40	$33.40
7 purchase totals =	$494.18		$532.8358	$532.83	$532.85	$532.90