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	$167.29	13.813%	$190.3978	$190.40	$190.40	$190.40
Purchase #2	$93.77	3.231%	$96.7997	$96.80	$96.80	$96.80
Purchase #3	$88.37	6.164%	$93.8171	$93.82	$93.80	$93.80
Purchase #4	$61.91	6.530%	$65.9527	$65.95	$65.95	$66.00
Purchase #5	$11.91	12.792%	$13.4335	$13.43	$13.45	$13.40
Purchase #6	$216.38	5.162%	$227.5495	$227.55	$227.55	$227.50
Purchase #7	$156.37	5.170%	$164.4543	$164.45	$164.45	$164.50
7 purchase totals =	$796.00		$852.4046	$852.40	$852.40	$852.40