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	$85.26	6.742%	$91.0082	$91.01	$91.00	$91.00
Purchase #2	$195.56	10.376%	$215.8513	$215.85	$215.85	$215.90
Purchase #3	$62.39	13.201%	$70.6261	$70.63	$70.65	$70.60
Purchase #4	$235.78	10.167%	$259.7518	$259.75	$259.75	$259.80
Purchase #5	$176.80	10.187%	$194.8106	$194.81	$194.80	$194.80
Purchase #6	$126.64	11.744%	$141.5126	$141.51	$141.50	$141.50
Purchase #7	$94.69	6.229%	$100.5882	$100.59	$100.60	$100.60
7 purchase totals =	$977.12		$1,074.1488	$1,074.15	$1,074.15	$1,074.20