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	$49.89	9.182%	$54.4709	$54.47	$54.45	$54.50
Purchase #2	$137.36	9.774%	$150.7856	$150.79	$150.80	$150.80
Purchase #3	$171.39	6.764%	$182.9828	$182.98	$183.00	$183.00
Purchase #4	$212.40	12.499%	$238.9479	$238.95	$238.95	$238.90
Purchase #5	$119.29	4.116%	$124.2	$124.20	$124.20	$124.20
Purchase #6	$150.66	10.852%	$167.0096	$167.01	$167.00	$167.00
Purchase #7	$134.86	11.414%	$150.2529	$150.25	$150.25	$150.30
7 purchase totals =	$975.85		$1,068.6497	$1,068.65	$1,068.65	$1,068.70