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	$126.37	12.631%	$142.3318	$142.33	$142.35	$142.30
Purchase #2	$153.86	6.809%	$164.3363	$164.34	$164.35	$164.30
Purchase #3	$11.27	4.584%	$11.7866	$11.79	$11.80	$11.80
Purchase #4	$9.85	4.299%	$10.2735	$10.27	$10.25	$10.30
Purchase #5	$173.82	6.473%	$185.0714	$185.07	$185.05	$185.10
Purchase #6	$125.80	3.774%	$130.5477	$130.55	$130.55	$130.50
Purchase #7	$25.38	13.849%	$28.8949	$28.89	$28.90	$28.90
7 purchase totals =	$626.35		$673.2422	$673.24	$673.25	$673.20