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	$13.45	10.647%	$14.882	$14.88	$14.90	$14.90
Purchase #2	$165.99	13.280%	$188.0335	$188.03	$188.05	$188.00
Purchase #3	$249.40	3.558%	$258.2737	$258.27	$258.25	$258.30
Purchase #4	$141.86	4.814%	$148.6891	$148.69	$148.70	$148.70
Purchase #5	$236.86	7.665%	$255.0153	$255.02	$255.00	$255.00
Purchase #6	$11.34	13.758%	$12.9002	$12.90	$12.90	$12.90
Purchase #7	$148.55	11.187%	$165.1683	$165.17	$165.15	$165.20
7 purchase totals =	$967.45		$1,042.9621	$1,042.96	$1,042.95	$1,043.00