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	$98.39	6.105%	$104.3967	$104.40	$104.40	$104.40
Purchase #2	$188.30	11.815%	$210.5476	$210.55	$210.55	$210.50
Purchase #3	$11.72	8.315%	$12.6945	$12.69	$12.70	$12.70
Purchase #4	$142.63	5.744%	$150.8227	$150.82	$150.80	$150.80
Purchase #5	$222.99	5.159%	$234.4941	$234.49	$234.50	$234.50
Purchase #6	$101.58	7.769%	$109.4718	$109.47	$109.45	$109.50
Purchase #7	$97.69	12.295%	$109.701	$109.70	$109.70	$109.70
7 purchase totals =	$863.30		$932.1284	$932.12	$932.10	$932.10