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	$151.88	11.183%	$168.8647	$168.86	$168.85	$168.90
Purchase #2	$246.71	13.676%	$280.4501	$280.45	$280.45	$280.50
Purchase #3	$199.88	4.639%	$209.1524	$209.15	$209.15	$209.20
Purchase #4	$34.60	8.751%	$37.6278	$37.63	$37.65	$37.60
Purchase #5	$249.69	5.458%	$263.3181	$263.32	$263.30	$263.30
Purchase #6	$162.32	5.555%	$171.3369	$171.34	$171.35	$171.30
Purchase #7	$16.97	5.503%	$17.9039	$17.90	$17.90	$17.90
7 purchase totals =	$1,062.05		$1,148.6539	$1,148.65	$1,148.65	$1,148.70