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	$155.88	5.501%	$164.455	$164.46	$164.45	$164.50
Purchase #2	$58.59	6.821%	$62.5864	$62.59	$62.60	$62.60
Purchase #3	$95.96	6.126%	$101.8385	$101.84	$101.85	$101.80
Purchase #4	$152.33	4.635%	$159.3905	$159.39	$159.40	$159.40
Purchase #5	$174.98	8.577%	$189.988	$189.99	$190.00	$190.00
Purchase #6	$229.88	8.582%	$249.6083	$249.61	$249.60	$249.60
Purchase #7	$13.76	5.150%	$14.4686	$14.47	$14.45	$14.50
7 purchase totals =	$881.38		$942.3353	$942.35	$942.35	$942.40