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	$191.70	4.610%	$200.5374	$200.54	$200.55	$200.50
Purchase #2	$145.55	12.809%	$164.1935	$164.19	$164.20	$164.20
Purchase #3	$80.37	11.800%	$89.8537	$89.85	$89.85	$89.90
Purchase #4	$43.88	5.585%	$46.3307	$46.33	$46.35	$46.30
Purchase #5	$146.78	7.446%	$157.7092	$157.71	$157.70	$157.70
Purchase #6	$75.42	7.190%	$80.8427	$80.84	$80.85	$80.80
Purchase #7	$198.32	7.479%	$213.1524	$213.15	$213.15	$213.20
7 purchase totals =	$882.02		$952.6196	$952.61	$952.65	$952.60