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	$48.44	13.107%	$54.789	$54.79	$54.80	$54.80
Purchase #2	$108.64	13.423%	$123.2227	$123.22	$123.20	$123.20
Purchase #3	$171.38	9.567%	$187.7759	$187.78	$187.80	$187.80
Purchase #4	$132.74	9.726%	$145.6503	$145.65	$145.65	$145.70
Purchase #5	$196.39	11.301%	$218.584	$218.58	$218.60	$218.60
Purchase #6	$150.40	11.605%	$167.8539	$167.85	$167.85	$167.90
Purchase #7	$219.39	12.570%	$246.9673	$246.97	$246.95	$247.00
7 purchase totals =	$1,027.38		$1,144.8431	$1,144.84	$1,144.85	$1,145.00