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	$75.80	11.225%	$84.3086	$84.31	$84.30	$84.30
Purchase #2	$163.45	9.616%	$179.1674	$179.17	$179.15	$179.20
Purchase #3	$62.94	10.271%	$69.4046	$69.40	$69.40	$69.40
Purchase #4	$155.84	4.540%	$162.9151	$162.92	$162.90	$162.90
Purchase #5	$72.79	7.312%	$78.1124	$78.11	$78.10	$78.10
Purchase #6	$70.34	11.451%	$78.3946	$78.39	$78.40	$78.40
Purchase #7	$179.59	9.440%	$196.5433	$196.54	$196.55	$196.50
7 purchase totals =	$780.75		$848.8460	$848.84	$848.80	$848.80