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	$219.39	13.432%	$248.8585	$248.86	$248.85	$248.90
Purchase #2	$63.72	6.102%	$67.6082	$67.61	$67.60	$67.60
Purchase #3	$121.59	3.332%	$125.6414	$125.64	$125.65	$125.60
Purchase #4	$151.73	9.475%	$166.1064	$166.11	$166.10	$166.10
Purchase #5	$41.41	3.353%	$42.7985	$42.80	$42.80	$42.80
Purchase #6	$164.45	4.453%	$171.773	$171.77	$171.75	$171.80
Purchase #7	$211.83	11.763%	$236.7476	$236.75	$236.75	$236.70
7 purchase totals =	$974.12		$1,059.5336	$1,059.54	$1,059.50	$1,059.50