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	$80.34	3.187%	$82.9004	$82.90	$82.90	$82.90
Purchase #2	$193.75	9.421%	$212.0032	$212.00	$212.00	$212.00
Purchase #3	$143.58	9.828%	$157.691	$157.69	$157.70	$157.70
Purchase #4	$87.90	13.141%	$99.4509	$99.45	$99.45	$99.50
Purchase #5	$160.41	5.281%	$168.8813	$168.88	$168.90	$168.90
Purchase #6	$93.86	6.720%	$100.1674	$100.17	$100.15	$100.20
Purchase #7	$61.88	4.663%	$64.7655	$64.77	$64.75	$64.80
7 purchase totals =	$821.72		$885.8597	$885.86	$885.85	$886.00