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	$233.83	9.760%	$256.6518	$256.65	$256.65	$256.70
Purchase #2	$214.66	10.863%	$237.9785	$237.98	$238.00	$238.00
Purchase #3	$10.66	12.811%	$12.0257	$12.03	$12.05	$12.00
Purchase #4	$52.86	9.623%	$57.9467	$57.95	$57.95	$57.90
Purchase #5	$203.63	9.313%	$222.5941	$222.59	$222.60	$222.60
Purchase #6	$181.33	4.402%	$189.3121	$189.31	$189.30	$189.30
Purchase #7	$24.87	12.872%	$28.0713	$28.07	$28.05	$28.10
7 purchase totals =	$921.84		$1,004.5802	$1,004.58	$1,004.60	$1,004.60