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	$238.94	4.846%	$250.519	$250.52	$250.50	$250.50
Purchase #2	$27.44	4.339%	$28.6306	$28.63	$28.65	$28.60
Purchase #3	$164.43	9.259%	$179.6546	$179.65	$179.65	$179.70
Purchase #4	$61.29	11.592%	$68.3947	$68.39	$68.40	$68.40
Purchase #5	$61.70	10.429%	$68.1347	$68.13	$68.15	$68.10
Purchase #6	$54.31	9.172%	$59.2913	$59.29	$59.30	$59.30
Purchase #7	$187.73	9.423%	$205.4198	$205.42	$205.40	$205.40
7 purchase totals =	$795.84		$860.0447	$860.03	$860.05	$860.00