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	$160.71	4.273%	$167.5771	$167.58	$167.60	$167.60
Purchase #2	$72.63	13.734%	$82.605	$82.61	$82.60	$82.60
Purchase #3	$83.88	3.603%	$86.9022	$86.90	$86.90	$86.90
Purchase #4	$249.34	12.397%	$280.2507	$280.25	$280.25	$280.30
Purchase #5	$148.99	5.311%	$156.9029	$156.90	$156.90	$156.90
Purchase #6	$203.91	8.449%	$221.1384	$221.14	$221.15	$221.10
Purchase #7	$183.85	6.750%	$196.2599	$196.26	$196.25	$196.30
7 purchase totals =	$1,103.31		$1,191.6362	$1,191.64	$1,191.65	$1,191.70