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	$129.38	4.207%	$134.823	$134.82	$134.80	$134.80
Purchase #2	$139.35	13.326%	$157.9198	$157.92	$157.90	$157.90
Purchase #3	$145.44	7.488%	$156.3305	$156.33	$156.35	$156.30
Purchase #4	$161.80	3.342%	$167.2074	$167.21	$167.20	$167.20
Purchase #5	$136.69	3.776%	$141.8514	$141.85	$141.85	$141.90
Purchase #6	$214.65	10.611%	$237.4265	$237.43	$237.45	$237.40
Purchase #7	$76.88	11.185%	$85.479	$85.48	$85.50	$85.50
7 purchase totals =	$1,004.19		$1,081.0376	$1,081.04	$1,081.05	$1,081.00