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	$52.57	13.442%	$59.6365	$59.64	$59.65	$59.60
Purchase #2	$219.99	3.790%	$228.3276	$228.33	$228.35	$228.30
Purchase #3	$167.69	11.204%	$186.478	$186.48	$186.50	$186.50
Purchase #4	$109.34	12.723%	$123.2513	$123.25	$123.25	$123.30
Purchase #5	$221.83	12.855%	$250.3462	$250.35	$250.35	$250.30
Purchase #6	$164.98	3.755%	$171.175	$171.18	$171.20	$171.20
Purchase #7	$202.59	6.305%	$215.3633	$215.36	$215.35	$215.40
7 purchase totals =	$1,138.99		$1,234.5779	$1,234.59	$1,234.65	$1,234.60