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	$182.30	4.674%	$190.8207	$190.82	$190.80	$190.80
Purchase #2	$72.32	7.695%	$77.885	$77.89	$77.90	$77.90
Purchase #3	$80.40	12.720%	$90.6269	$90.63	$90.65	$90.60
Purchase #4	$76.90	5.868%	$81.4125	$81.41	$81.40	$81.40
Purchase #5	$164.93	11.360%	$183.666	$183.67	$183.65	$183.70
Purchase #6	$158.31	7.124%	$169.588	$169.59	$169.60	$169.60
Purchase #7	$204.29	12.851%	$230.5433	$230.54	$230.55	$230.50
7 purchase totals =	$939.45		$1,024.5424	$1,024.55	$1,024.55	$1,024.50