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	$224.76	3.209%	$231.9725	$231.97	$231.95	$232.00
Purchase #2	$145.45	9.836%	$159.7565	$159.76	$159.75	$159.80
Purchase #3	$37.81	4.513%	$39.5164	$39.52	$39.50	$39.50
Purchase #4	$17.96	13.726%	$20.4252	$20.43	$20.45	$20.40
Purchase #5	$198.97	10.517%	$219.8957	$219.90	$219.90	$219.90
Purchase #6	$207.38	10.623%	$229.41	$229.41	$229.40	$229.40
Purchase #7	$91.44	9.803%	$100.4039	$100.40	$100.40	$100.40
7 purchase totals =	$923.77		$1,001.3802	$1,001.39	$1,001.35	$1,001.40