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	$244.50	6.137%	$259.505	$259.51	$259.50	$259.50
Purchase #2	$225.70	4.632%	$236.1544	$236.15	$236.15	$236.20
Purchase #3	$45.34	3.166%	$46.7755	$46.78	$46.80	$46.80
Purchase #4	$69.44	12.731%	$78.2804	$78.28	$78.30	$78.30
Purchase #5	$226.86	12.778%	$255.8482	$255.85	$255.85	$255.80
Purchase #6	$114.52	9.358%	$125.2368	$125.24	$125.25	$125.20
Purchase #7	$86.92	4.208%	$90.5776	$90.58	$90.60	$90.60
7 purchase totals =	$1,013.28		$1,092.3779	$1,092.39	$1,092.45	$1,092.40