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	$183.32	4.719%	$191.9709	$191.97	$191.95	$192.00
Purchase #2	$161.85	9.130%	$176.6269	$176.63	$176.65	$176.60
Purchase #3	$95.53	6.598%	$101.8331	$101.83	$101.85	$101.80
Purchase #4	$78.36	9.116%	$85.5033	$85.50	$85.50	$85.50
Purchase #5	$231.45	4.702%	$242.3328	$242.33	$242.35	$242.30
Purchase #6	$18.37	12.116%	$20.5957	$20.60	$20.60	$20.60
Purchase #7	$61.30	10.206%	$67.5563	$67.56	$67.55	$67.60
7 purchase totals =	$830.18		$886.4190	$886.42	$886.45	$886.40