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	$199.91	11.328%	$222.5558	$222.56	$222.55	$222.60
Purchase #2	$124.87	12.357%	$140.3002	$140.30	$140.30	$140.30
Purchase #3	$229.83	7.838%	$247.8441	$247.84	$247.85	$247.80
Purchase #4	$183.43	4.155%	$191.0515	$191.05	$191.05	$191.10
Purchase #5	$45.43	13.269%	$51.4581	$51.46	$51.45	$51.50
Purchase #6	$29.33	7.348%	$31.4852	$31.49	$31.50	$31.50
Purchase #7	$156.36	5.207%	$164.5017	$164.50	$164.50	$164.50
7 purchase totals =	$969.16		$1,049.1966	$1,049.20	$1,049.20	$1,049.30