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	$63.39	11.405%	$70.6196	$70.62	$70.60	$70.60
Purchase #2	$162.71	3.124%	$167.7931	$167.79	$167.80	$167.80
Purchase #3	$181.89	6.460%	$193.6401	$193.64	$193.65	$193.60
Purchase #4	$161.94	7.827%	$174.615	$174.62	$174.60	$174.60
Purchase #5	$165.56	8.856%	$180.222	$180.22	$180.20	$180.20
Purchase #6	$152.76	12.296%	$171.5434	$171.54	$171.55	$171.50
Purchase #7	$41.37	12.325%	$46.4689	$46.47	$46.45	$46.50
7 purchase totals =	$929.62		$1,004.9021	$1,004.90	$1,004.85	$1,004.80