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	$42.39	5.261%	$44.6201	$44.62	$44.60	$44.60
Purchase #2	$146.36	12.412%	$164.5262	$164.53	$164.55	$164.50
Purchase #3	$228.66	12.464%	$257.1602	$257.16	$257.15	$257.20
Purchase #4	$91.65	8.320%	$99.2753	$99.28	$99.30	$99.30
Purchase #5	$115.41	9.812%	$126.734	$126.73	$126.75	$126.70
Purchase #6	$244.55	4.636%	$255.8873	$255.89	$255.90	$255.90
Purchase #7	$184.94	7.240%	$198.3297	$198.33	$198.35	$198.30
7 purchase totals =	$1,053.96		$1,146.5328	$1,146.54	$1,146.60	$1,146.50