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	$238.86	4.391%	$249.3483	$249.35	$249.35	$249.30
Purchase #2	$177.27	3.810%	$184.024	$184.02	$184.00	$184.00
Purchase #3	$108.38	13.567%	$123.0839	$123.08	$123.10	$123.10
Purchase #4	$217.60	12.620%	$245.0611	$245.06	$245.05	$245.10
Purchase #5	$180.62	7.390%	$193.9678	$193.97	$193.95	$194.00
Purchase #6	$177.71	10.769%	$196.8476	$196.85	$196.85	$196.80
Purchase #7	$123.85	11.334%	$137.8872	$137.89	$137.90	$137.90
7 purchase totals =	$1,224.29		$1,330.2199	$1,330.22	$1,330.20	$1,330.20