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	$177.76	12.689%	$200.316	$200.32	$200.30	$200.30
Purchase #2	$77.41	11.711%	$86.4755	$86.48	$86.50	$86.50
Purchase #3	$43.86	10.215%	$48.3403	$48.34	$48.35	$48.30
Purchase #4	$97.63	12.147%	$109.4891	$109.49	$109.50	$109.50
Purchase #5	$198.53	13.608%	$225.546	$225.55	$225.55	$225.50
Purchase #6	$129.56	8.268%	$140.272	$140.27	$140.25	$140.30
Purchase #7	$165.27	13.541%	$187.6492	$187.65	$187.65	$187.60
7 purchase totals =	$890.02		$998.0881	$998.10	$998.10	$998.00