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	$186.63	4.189%	$194.4479	$194.45	$194.45	$194.40
Purchase #2	$159.54	3.153%	$164.5703	$164.57	$164.55	$164.60
Purchase #3	$66.56	8.737%	$72.3753	$72.38	$72.40	$72.40
Purchase #4	$185.54	8.233%	$200.8155	$200.82	$200.80	$200.80
Purchase #5	$87.85	6.657%	$93.6982	$93.70	$93.70	$93.70
Purchase #6	$29.81	12.325%	$33.4841	$33.48	$33.50	$33.50
Purchase #7	$19.33	11.102%	$21.476	$21.48	$21.50	$21.50
7 purchase totals =	$735.26		$780.8673	$780.88	$780.90	$780.90