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	$130.75	5.230%	$137.5882	$137.59	$137.60	$137.60
Purchase #2	$124.90	12.526%	$140.545	$140.55	$140.55	$140.50
Purchase #3	$207.48	7.513%	$223.068	$223.07	$223.05	$223.10
Purchase #4	$100.57	8.785%	$109.4051	$109.41	$109.40	$109.40
Purchase #5	$196.40	3.162%	$202.6102	$202.61	$202.60	$202.60
Purchase #6	$143.48	9.406%	$156.9757	$156.98	$157.00	$157.00
Purchase #7	$223.54	4.799%	$234.2677	$234.27	$234.25	$234.30
7 purchase totals =	$1,127.12		$1,204.4599	$1,204.48	$1,204.45	$1,204.50