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	$81.63	9.587%	$89.4559	$89.46	$89.45	$89.50
Purchase #2	$22.66	12.504%	$25.4934	$25.49	$25.50	$25.50
Purchase #3	$153.94	9.615%	$168.7413	$168.74	$168.75	$168.70
Purchase #4	$232.43	5.688%	$245.6506	$245.65	$245.65	$245.70
Purchase #5	$194.42	12.542%	$218.8042	$218.80	$218.80	$218.80
Purchase #6	$194.56	5.626%	$205.5059	$205.51	$205.50	$205.50
Purchase #7	$243.76	5.354%	$256.8109	$256.81	$256.80	$256.80
7 purchase totals =	$1,123.40		$1,210.4622	$1,210.46	$1,210.45	$1,210.50