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	$213.32	6.616%	$227.4333	$227.43	$227.45	$227.40
Purchase #2	$185.27	9.111%	$202.1499	$202.15	$202.15	$202.10
Purchase #3	$216.27	3.538%	$223.9216	$223.92	$223.90	$223.90
Purchase #4	$87.82	11.716%	$98.109	$98.11	$98.10	$98.10
Purchase #5	$184.49	6.741%	$196.9265	$196.93	$196.95	$196.90
Purchase #6	$72.63	11.213%	$80.774	$80.77	$80.75	$80.80
Purchase #7	$11.82	11.276%	$13.1528	$13.15	$13.15	$13.20
7 purchase totals =	$971.62		$1,042.4671	$1,042.46	$1,042.45	$1,042.40