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	$54.42	9.151%	$59.4	$59.40	$59.40	$59.40
Purchase #2	$105.38	6.135%	$111.8451	$111.85	$111.85	$111.80
Purchase #3	$29.85	7.454%	$32.075	$32.08	$32.10	$32.10
Purchase #4	$54.45	3.684%	$56.4559	$56.46	$56.45	$56.50
Purchase #5	$127.73	7.832%	$137.7338	$137.73	$137.75	$137.70
Purchase #6	$178.83	4.306%	$186.5304	$186.53	$186.55	$186.50
Purchase #7	$104.84	5.376%	$110.4762	$110.48	$110.50	$110.50
7 purchase totals =	$655.50		$694.5164	$694.53	$694.60	$694.50