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	$164.82	3.617%	$170.7815	$170.78	$170.80	$170.80
Purchase #2	$111.25	12.246%	$124.8737	$124.87	$124.85	$124.90
Purchase #3	$144.38	13.815%	$164.3261	$164.33	$164.35	$164.30
Purchase #4	$181.74	13.102%	$205.5516	$205.55	$205.55	$205.60
Purchase #5	$157.99	5.102%	$166.0506	$166.05	$166.05	$166.10
Purchase #6	$67.31	8.796%	$73.2306	$73.23	$73.25	$73.20
Purchase #7	$117.40	8.666%	$127.5739	$127.57	$127.55	$127.60
7 purchase totals =	$944.89		$1,032.3880	$1,032.38	$1,032.40	$1,032.50