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	$95.82	3.680%	$99.3462	$99.35	$99.35	$99.30
Purchase #2	$69.76	3.786%	$72.4011	$72.40	$72.40	$72.40
Purchase #3	$83.98	10.414%	$92.7257	$92.73	$92.75	$92.70
Purchase #4	$5.36	12.750%	$6.0434	$6.04	$6.05	$6.00
Purchase #5	$160.85	4.143%	$167.514	$167.51	$167.50	$167.50
Purchase #6	$164.86	9.508%	$180.5349	$180.53	$180.55	$180.50
Purchase #7	$37.96	7.620%	$40.8526	$40.85	$40.85	$40.90
7 purchase totals =	$618.59		$659.4179	$659.41	$659.45	$659.30