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	$68.77	13.524%	$78.0705	$78.07	$78.05	$78.10
Purchase #2	$10.63	12.392%	$11.9473	$11.95	$11.95	$11.90
Purchase #3	$51.98	9.252%	$56.7892	$56.79	$56.80	$56.80
Purchase #4	$121.98	13.442%	$138.3766	$138.38	$138.40	$138.40
Purchase #5	$178.85	3.502%	$185.1133	$185.11	$185.10	$185.10
Purchase #6	$148.87	13.211%	$168.5372	$168.54	$168.55	$168.50
Purchase #7	$38.40	13.615%	$43.6282	$43.63	$43.65	$43.60
7 purchase totals =	$619.48		$682.4623	$682.47	$682.50	$682.40