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	$17.39	5.317%	$18.3146	$18.31	$18.30	$18.30
Purchase #2	$68.90	5.770%	$72.8755	$72.88	$72.90	$72.90
Purchase #3	$127.82	12.272%	$143.5061	$143.51	$143.50	$143.50
Purchase #4	$26.37	13.278%	$29.8714	$29.87	$29.85	$29.90
Purchase #5	$191.36	7.577%	$205.8593	$205.86	$205.85	$205.90
Purchase #6	$41.56	13.477%	$47.161	$47.16	$47.15	$47.20
Purchase #7	$195.38	5.244%	$205.6257	$205.63	$205.65	$205.60
7 purchase totals =	$668.78		$723.2136	$723.22	$723.20	$723.30