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	$47.59	10.359%	$52.5198	$52.52	$52.50	$52.50
Purchase #2	$165.67	11.390%	$184.5398	$184.54	$184.55	$184.50
Purchase #3	$80.74	4.118%	$84.0649	$84.06	$84.05	$84.10
Purchase #4	$148.33	11.746%	$165.7528	$165.75	$165.75	$165.80
Purchase #5	$23.36	9.346%	$25.5432	$25.54	$25.55	$25.50
Purchase #6	$42.57	12.864%	$48.0462	$48.05	$48.05	$48.00
Purchase #7	$189.25	3.612%	$196.0857	$196.09	$196.10	$196.10
7 purchase totals =	$697.51		$756.5524	$756.55	$756.55	$756.50