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	$144.39	12.598%	$162.5803	$162.58	$162.60	$162.60
Purchase #2	$86.48	3.382%	$89.4048	$89.40	$89.40	$89.40
Purchase #3	$59.41	6.206%	$63.097	$63.10	$63.10	$63.10
Purchase #4	$75.86	6.252%	$80.6028	$80.60	$80.60	$80.60
Purchase #5	$222.44	8.271%	$240.838	$240.84	$240.85	$240.80
Purchase #6	$49.99	3.261%	$51.6202	$51.62	$51.60	$51.60
Purchase #7	$101.28	12.181%	$113.6169	$113.62	$113.60	$113.60
7 purchase totals =	$739.85		$801.7600	$801.76	$801.75	$801.70