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	$163.42	10.808%	$181.0824	$181.08	$181.10	$181.10
Purchase #2	$69.85	3.261%	$72.1278	$72.13	$72.15	$72.10
Purchase #3	$64.73	4.206%	$67.4525	$67.45	$67.45	$67.50
Purchase #4	$156.46	4.399%	$163.3427	$163.34	$163.35	$163.30
Purchase #5	$54.37	8.638%	$59.0665	$59.07	$59.05	$59.10
Purchase #6	$55.50	8.645%	$60.298	$60.30	$60.30	$60.30
Purchase #7	$165.39	12.486%	$186.0406	$186.04	$186.05	$186.00
7 purchase totals =	$729.72		$789.4105	$789.41	$789.45	$789.40