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	$85.37	4.783%	$89.4532	$89.45	$89.45	$89.50
Purchase #2	$23.41	4.826%	$24.5398	$24.54	$24.55	$24.50
Purchase #3	$104.55	5.645%	$110.4518	$110.45	$110.45	$110.50
Purchase #4	$182.60	6.225%	$193.9669	$193.97	$193.95	$194.00
Purchase #5	$123.42	6.572%	$131.5312	$131.53	$131.55	$131.50
Purchase #6	$126.73	4.349%	$132.2415	$132.24	$132.25	$132.20
Purchase #7	$207.29	7.211%	$222.2377	$222.24	$222.25	$222.20
7 purchase totals =	$853.37		$904.4221	$904.42	$904.45	$904.40