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	$52.95	8.112%	$57.2453	$57.25	$57.25	$57.20
Purchase #2	$250.85	12.602%	$282.4621	$282.46	$282.45	$282.50
Purchase #3	$157.64	5.687%	$166.605	$166.61	$166.60	$166.60
Purchase #4	$42.98	6.121%	$45.6108	$45.61	$45.60	$45.60
Purchase #5	$148.82	7.473%	$159.9413	$159.94	$159.95	$159.90
Purchase #6	$207.78	9.707%	$227.9492	$227.95	$227.95	$227.90
Purchase #7	$246.37	3.631%	$255.3157	$255.32	$255.30	$255.30
7 purchase totals =	$1,107.39		$1,195.1294	$1,195.14	$1,195.10	$1,195.00