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	$196.88	10.511%	$217.5741	$217.57	$217.55	$217.60
Purchase #2	$94.80	10.299%	$104.5635	$104.56	$104.55	$104.60
Purchase #3	$12.58	9.502%	$13.7754	$13.78	$13.80	$13.80
Purchase #4	$111.86	7.482%	$120.2294	$120.23	$120.25	$120.20
Purchase #5	$84.59	7.397%	$90.8471	$90.85	$90.85	$90.80
Purchase #6	$138.98	3.260%	$143.5107	$143.51	$143.50	$143.50
Purchase #7	$100.94	8.760%	$109.7823	$109.78	$109.80	$109.80
7 purchase totals =	$740.63		$800.2825	$800.28	$800.30	$800.30