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	$198.28	7.874%	$213.8926	$213.89	$213.90	$213.90
Purchase #2	$93.71	5.184%	$98.5679	$98.57	$98.55	$98.60
Purchase #3	$248.32	4.428%	$259.3156	$259.32	$259.30	$259.30
Purchase #4	$173.96	11.309%	$193.6331	$193.63	$193.65	$193.60
Purchase #5	$187.42	11.460%	$208.8983	$208.90	$208.90	$208.90
Purchase #6	$13.50	4.631%	$14.1252	$14.13	$14.15	$14.10
Purchase #7	$85.52	5.218%	$89.9824	$89.98	$90.00	$90.00
7 purchase totals =	$1,000.71		$1,078.4151	$1,078.42	$1,078.45	$1,078.40