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	$182.47	12.561%	$205.3901	$205.39	$205.40	$205.40
Purchase #2	$78.94	4.344%	$82.3692	$82.37	$82.35	$82.40
Purchase #3	$61.89	3.735%	$64.2016	$64.20	$64.20	$64.20
Purchase #4	$91.88	8.149%	$99.3673	$99.37	$99.35	$99.40
Purchase #5	$134.86	5.711%	$142.5619	$142.56	$142.55	$142.60
Purchase #6	$232.35	11.543%	$259.1702	$259.17	$259.15	$259.20
Purchase #7	$96.36	9.771%	$105.7753	$105.78	$105.80	$105.80
7 purchase totals =	$878.75		$958.8356	$958.84	$958.80	$959.00