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	$57.95	12.770%	$65.3502	$65.35	$65.35	$65.40
Purchase #2	$84.51	6.747%	$90.2119	$90.21	$90.20	$90.20
Purchase #3	$189.81	12.853%	$214.2063	$214.21	$214.20	$214.20
Purchase #4	$78.76	9.841%	$86.5108	$86.51	$86.50	$86.50
Purchase #5	$178.41	12.336%	$200.4187	$200.42	$200.40	$200.40
Purchase #6	$55.64	7.470%	$59.7963	$59.80	$59.80	$59.80
Purchase #7	$231.34	6.708%	$246.8583	$246.86	$246.85	$246.90
7 purchase totals =	$876.42		$963.3525	$963.36	$963.30	$963.40