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	$23.85	7.261%	$25.5817	$25.58	$25.60	$25.60
Purchase #2	$45.71	4.761%	$47.8863	$47.89	$47.90	$47.90
Purchase #3	$141.72	5.539%	$149.5699	$149.57	$149.55	$149.60
Purchase #4	$52.83	5.338%	$55.6501	$55.65	$55.65	$55.70
Purchase #5	$207.94	7.201%	$222.9138	$222.91	$222.90	$222.90
Purchase #6	$243.37	9.403%	$266.2541	$266.25	$266.25	$266.30
Purchase #7	$55.27	4.690%	$57.8622	$57.86	$57.85	$57.90
7 purchase totals =	$770.69		$825.7181	$825.71	$825.70	$825.90