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	$141.88	4.639%	$148.4618	$148.46	$148.45	$148.50
Purchase #2	$174.62	11.183%	$194.1478	$194.15	$194.15	$194.10
Purchase #3	$165.71	11.439%	$184.6656	$184.67	$184.65	$184.70
Purchase #4	$130.64	13.459%	$148.2228	$148.22	$148.20	$148.20
Purchase #5	$176.31	11.214%	$196.0814	$196.08	$196.10	$196.10
Purchase #6	$28.81	9.258%	$31.4772	$31.48	$31.50	$31.50
Purchase #7	$152.99	10.492%	$169.0417	$169.04	$169.05	$169.00
7 purchase totals =	$970.96		$1,072.0983	$1,072.10	$1,072.10	$1,072.10