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	$157.78	13.243%	$178.6748	$178.67	$178.65	$178.70
Purchase #2	$180.69	3.206%	$186.4829	$186.48	$186.50	$186.50
Purchase #3	$86.74	10.429%	$95.7861	$95.79	$95.80	$95.80
Purchase #4	$237.29	10.482%	$262.1627	$262.16	$262.15	$262.20
Purchase #5	$179.36	6.238%	$190.5485	$190.55	$190.55	$190.50
Purchase #6	$10.42	8.533%	$11.3091	$11.31	$11.30	$11.30
Purchase #7	$123.69	3.336%	$127.8163	$127.82	$127.80	$127.80
7 purchase totals =	$975.97		$1,052.7804	$1,052.78	$1,052.75	$1,052.80