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	$54.27	9.148%	$59.2346	$59.23	$59.25	$59.20
Purchase #2	$165.97	9.110%	$181.0899	$181.09	$181.10	$181.10
Purchase #3	$50.75	9.413%	$55.5271	$55.53	$55.55	$55.50
Purchase #4	$248.34	4.286%	$258.9839	$258.98	$259.00	$259.00
Purchase #5	$45.89	13.136%	$51.9181	$51.92	$51.90	$51.90
Purchase #6	$194.86	12.558%	$219.3305	$219.33	$219.35	$219.30
Purchase #7	$83.68	7.713%	$90.1342	$90.13	$90.15	$90.10
7 purchase totals =	$843.76		$916.2183	$916.21	$916.30	$916.10