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	$246.28	8.745%	$267.8172	$267.82	$267.80	$267.80
Purchase #2	$191.59	6.837%	$204.689	$204.69	$204.70	$204.70
Purchase #3	$242.89	12.318%	$272.8092	$272.81	$272.80	$272.80
Purchase #4	$106.39	3.606%	$110.2264	$110.23	$110.25	$110.20
Purchase #5	$28.45	10.405%	$31.4102	$31.41	$31.40	$31.40
Purchase #6	$15.79	10.829%	$17.4999	$17.50	$17.50	$17.50
Purchase #7	$173.28	13.429%	$196.5498	$196.55	$196.55	$196.50
7 purchase totals =	$1,004.67		$1,101.0017	$1,101.01	$1,101.00	$1,100.90