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	$159.25	9.298%	$174.0571	$174.06	$174.05	$174.10
Purchase #2	$213.79	7.505%	$229.8349	$229.83	$229.85	$229.80
Purchase #3	$168.66	11.828%	$188.6091	$188.61	$188.60	$188.60
Purchase #4	$82.57	10.455%	$91.2027	$91.20	$91.20	$91.20
Purchase #5	$78.36	5.134%	$82.383	$82.38	$82.40	$82.40
Purchase #6	$152.52	5.450%	$160.8323	$160.83	$160.85	$160.80
Purchase #7	$136.54	9.763%	$149.8704	$149.87	$149.85	$149.90
7 purchase totals =	$991.69		$1,076.7895	$1,076.78	$1,076.80	$1,076.80