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	$182.63	8.577%	$198.2942	$198.29	$198.30	$198.30
Purchase #2	$209.50	10.522%	$231.5436	$231.54	$231.55	$231.50
Purchase #3	$64.34	13.294%	$72.8934	$72.89	$72.90	$72.90
Purchase #4	$192.27	3.423%	$198.8514	$198.85	$198.85	$198.90
Purchase #5	$175.27	11.412%	$195.2718	$195.27	$195.25	$195.30
Purchase #6	$176.83	9.656%	$193.9047	$193.90	$193.90	$193.90
Purchase #7	$7.37	5.847%	$7.8009	$7.80	$7.80	$7.80
7 purchase totals =	$1,008.21		$1,098.5600	$1,098.54	$1,098.55	$1,098.60