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	$116.45	9.488%	$127.4988	$127.50	$127.50	$127.50
Purchase #2	$200.60	6.391%	$213.4203	$213.42	$213.40	$213.40
Purchase #3	$118.89	3.773%	$123.3757	$123.38	$123.40	$123.40
Purchase #4	$152.54	8.517%	$165.5318	$165.53	$165.55	$165.50
Purchase #5	$26.78	13.121%	$30.2938	$30.29	$30.30	$30.30
Purchase #6	$110.79	6.248%	$117.7122	$117.71	$117.70	$117.70
Purchase #7	$86.84	13.419%	$98.4931	$98.49	$98.50	$98.50
7 purchase totals =	$812.89		$876.3257	$876.32	$876.35	$876.30