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	$46.90	10.672%	$51.9052	$51.91	$51.90	$51.90
Purchase #2	$99.27	6.241%	$105.4654	$105.47	$105.45	$105.50
Purchase #3	$199.57	5.555%	$210.6561	$210.66	$210.65	$210.70
Purchase #4	$55.62	9.832%	$61.0886	$61.09	$61.10	$61.10
Purchase #5	$146.94	6.582%	$156.6116	$156.61	$156.60	$156.60
Purchase #6	$206.29	12.307%	$231.6781	$231.68	$231.70	$231.70
Purchase #7	$229.96	5.331%	$242.2192	$242.22	$242.20	$242.20
7 purchase totals =	$984.55		$1,059.6242	$1,059.64	$1,059.60	$1,059.70