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	$231.38	11.313%	$257.556	$257.56	$257.55	$257.60
Purchase #2	$126.61	8.304%	$137.1237	$137.12	$137.10	$137.10
Purchase #3	$65.55	12.358%	$73.6507	$73.65	$73.65	$73.70
Purchase #4	$71.73	9.317%	$78.4131	$78.41	$78.40	$78.40
Purchase #5	$215.89	5.719%	$228.2367	$228.24	$228.25	$228.20
Purchase #6	$165.57	6.686%	$176.64	$176.64	$176.65	$176.60
Purchase #7	$104.98	5.785%	$111.0531	$111.05	$111.05	$111.10
7 purchase totals =	$981.71		$1,062.6733	$1,062.67	$1,062.65	$1,062.70