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	$89.61	3.262%	$92.5331	$92.53	$92.55	$92.50
Purchase #2	$221.55	7.342%	$237.8162	$237.82	$237.80	$237.80
Purchase #3	$66.59	9.480%	$72.9027	$72.90	$72.90	$72.90
Purchase #4	$50.45	4.333%	$52.636	$52.64	$52.65	$52.60
Purchase #5	$250.79	4.665%	$262.4894	$262.49	$262.50	$262.50
Purchase #6	$141.33	5.660%	$149.3293	$149.33	$149.35	$149.30
Purchase #7	$73.75	12.483%	$82.9562	$82.96	$82.95	$83.00
7 purchase totals =	$894.07		$950.6629	$950.67	$950.70	$950.60