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	$35.49	8.589%	$38.5382	$38.54	$38.55	$38.50
Purchase #2	$212.50	7.336%	$228.089	$228.09	$228.10	$228.10
Purchase #3	$165.58	3.847%	$171.9499	$171.95	$171.95	$171.90
Purchase #4	$244.28	7.134%	$261.7069	$261.71	$261.70	$261.70
Purchase #5	$187.78	4.457%	$196.1494	$196.15	$196.15	$196.10
Purchase #6	$36.87	12.477%	$41.4703	$41.47	$41.45	$41.50
Purchase #7	$238.93	9.700%	$262.1062	$262.11	$262.10	$262.10
7 purchase totals =	$1,121.43		$1,200.0099	$1,200.02	$1,200.00	$1,199.90