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	$66.98	6.806%	$71.5387	$71.54	$71.55	$71.50
Purchase #2	$182.37	5.594%	$192.5718	$192.57	$192.55	$192.60
Purchase #3	$94.56	8.265%	$102.3754	$102.38	$102.40	$102.40
Purchase #4	$200.98	7.637%	$216.3288	$216.33	$216.35	$216.30
Purchase #5	$93.54	10.686%	$103.5357	$103.54	$103.55	$103.50
Purchase #6	$83.62	13.736%	$95.106	$95.11	$95.10	$95.10
Purchase #7	$14.75	4.228%	$15.3736	$15.37	$15.35	$15.40
7 purchase totals =	$736.80		$796.8300	$796.84	$796.85	$796.80