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	$152.87	7.361%	$164.1228	$164.12	$164.10	$164.10
Purchase #2	$139.51	13.641%	$158.5406	$158.54	$158.55	$158.50
Purchase #3	$153.86	11.390%	$171.3847	$171.38	$171.40	$171.40
Purchase #4	$211.88	4.329%	$221.0523	$221.05	$221.05	$221.10
Purchase #5	$166.81	7.472%	$179.274	$179.27	$179.25	$179.30
Purchase #6	$76.62	7.868%	$82.6485	$82.65	$82.65	$82.60
Purchase #7	$95.48	4.528%	$99.8033	$99.80	$99.80	$99.80
7 purchase totals =	$997.03		$1,076.8262	$1,076.81	$1,076.80	$1,076.80