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	$224.55	11.627%	$250.6584	$250.66	$250.65	$250.70
Purchase #2	$119.45	9.524%	$130.8264	$130.83	$130.85	$130.80
Purchase #3	$141.82	6.376%	$150.8624	$150.86	$150.85	$150.90
Purchase #4	$93.85	13.654%	$106.6643	$106.66	$106.65	$106.70
Purchase #5	$88.99	4.446%	$92.9465	$92.95	$92.95	$92.90
Purchase #6	$177.45	7.120%	$190.0844	$190.08	$190.10	$190.10
Purchase #7	$196.68	13.283%	$222.805	$222.81	$222.80	$222.80
7 purchase totals =	$1,042.79		$1,144.8474	$1,144.85	$1,144.85	$1,144.90