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	$72.82	5.590%	$76.8906	$76.89	$76.90	$76.90
Purchase #2	$41.38	4.359%	$43.1838	$43.18	$43.20	$43.20
Purchase #3	$188.63	11.295%	$209.9358	$209.94	$209.95	$209.90
Purchase #4	$160.76	9.783%	$176.4872	$176.49	$176.50	$176.50
Purchase #5	$179.36	11.210%	$199.4663	$199.47	$199.45	$199.50
Purchase #6	$167.92	13.720%	$190.9586	$190.96	$190.95	$191.00
Purchase #7	$85.82	3.852%	$89.1258	$89.13	$89.15	$89.10
7 purchase totals =	$896.69		$986.0481	$986.06	$986.10	$986.10