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	$148.96	13.737%	$169.4226	$169.42	$169.40	$169.40
Purchase #2	$98.47	11.567%	$109.86	$109.86	$109.85	$109.90
Purchase #3	$210.27	12.267%	$236.0638	$236.06	$236.05	$236.10
Purchase #4	$140.38	7.771%	$151.2889	$151.29	$151.30	$151.30
Purchase #5	$170.86	9.158%	$186.5074	$186.51	$186.50	$186.50
Purchase #6	$7.63	11.418%	$8.5012	$8.50	$8.50	$8.50
Purchase #7	$39.63	9.340%	$43.3314	$43.33	$43.35	$43.30
7 purchase totals =	$816.20		$904.9753	$904.97	$904.95	$905.00