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	$148.27	13.227%	$167.8817	$167.88	$167.90	$167.90
Purchase #2	$45.83	7.440%	$49.2398	$49.24	$49.25	$49.20
Purchase #3	$152.61	7.688%	$164.3427	$164.34	$164.35	$164.30
Purchase #4	$140.78	7.211%	$150.9316	$150.93	$150.95	$150.90
Purchase #5	$67.87	6.143%	$72.0393	$72.04	$72.05	$72.00
Purchase #6	$82.78	13.272%	$93.7666	$93.77	$93.75	$93.80
Purchase #7	$63.26	6.234%	$67.2036	$67.20	$67.20	$67.20
7 purchase totals =	$701.40		$765.4053	$765.40	$765.45	$765.30