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	$222.77	10.827%	$246.8893	$246.89	$246.90	$246.90
Purchase #2	$46.54	6.347%	$49.4939	$49.49	$49.50	$49.50
Purchase #3	$33.86	11.589%	$37.784	$37.78	$37.80	$37.80
Purchase #4	$249.25	3.824%	$258.7813	$258.78	$258.80	$258.80
Purchase #5	$175.83	12.706%	$198.171	$198.17	$198.15	$198.20
Purchase #6	$205.58	6.153%	$218.2293	$218.23	$218.25	$218.20
Purchase #7	$78.48	3.628%	$81.3273	$81.33	$81.35	$81.30
7 purchase totals =	$1,012.31		$1,090.6761	$1,090.67	$1,090.75	$1,090.70