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	$196.56	13.621%	$223.3334	$223.33	$223.35	$223.30
Purchase #2	$162.46	7.671%	$174.9223	$174.92	$174.90	$174.90
Purchase #3	$203.98	13.453%	$231.4214	$231.42	$231.40	$231.40
Purchase #4	$98.99	5.316%	$104.2523	$104.25	$104.25	$104.30
Purchase #5	$76.82	7.865%	$82.8619	$82.86	$82.85	$82.90
Purchase #6	$227.50	4.725%	$238.2494	$238.25	$238.25	$238.20
Purchase #7	$194.60	12.324%	$218.5825	$218.58	$218.60	$218.60
7 purchase totals =	$1,160.91		$1,273.6232	$1,273.61	$1,273.60	$1,273.60