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	$226.27	9.338%	$247.3991	$247.40	$247.40	$247.40
Purchase #2	$151.86	10.134%	$167.2495	$167.25	$167.25	$167.20
Purchase #3	$19.41	12.618%	$21.8592	$21.86	$21.85	$21.90
Purchase #4	$169.86	9.137%	$185.3801	$185.38	$185.40	$185.40
Purchase #5	$190.92	4.600%	$199.7023	$199.70	$199.70	$199.70
Purchase #6	$215.69	13.767%	$245.384	$245.38	$245.40	$245.40
Purchase #7	$188.65	9.678%	$206.9075	$206.91	$206.90	$206.90
7 purchase totals =	$1,162.66		$1,273.8817	$1,273.88	$1,273.90	$1,273.90