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	$68.43	9.560%	$74.9719	$74.97	$74.95	$75.00
Purchase #2	$154.52	6.758%	$164.9625	$164.96	$164.95	$165.00
Purchase #3	$106.25	4.860%	$111.4138	$111.41	$111.40	$111.40
Purchase #4	$38.75	11.229%	$43.1012	$43.10	$43.10	$43.10
Purchase #5	$246.97	3.261%	$255.0237	$255.02	$255.00	$255.00
Purchase #6	$220.96	4.650%	$231.2346	$231.23	$231.25	$231.20
Purchase #7	$192.99	11.617%	$215.4096	$215.41	$215.40	$215.40
7 purchase totals =	$1,028.87		$1,096.1173	$1,096.10	$1,096.05	$1,096.10