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	$218.31	6.130%	$231.6924	$231.69	$231.70	$231.70
Purchase #2	$128.52	9.571%	$140.8206	$140.82	$140.80	$140.80
Purchase #3	$174.34	4.786%	$182.6839	$182.68	$182.70	$182.70
Purchase #4	$54.96	8.721%	$59.7531	$59.75	$59.75	$59.80
Purchase #5	$217.67	7.245%	$233.4402	$233.44	$233.45	$233.40
Purchase #6	$39.71	7.130%	$42.5413	$42.54	$42.55	$42.50
Purchase #7	$203.55	5.404%	$214.5498	$214.55	$214.55	$214.50
7 purchase totals =	$1,037.06		$1,105.4813	$1,105.47	$1,105.50	$1,105.40