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	$249.65	4.330%	$260.4598	$260.46	$260.45	$260.50
Purchase #2	$84.67	6.701%	$90.3437	$90.34	$90.35	$90.30
Purchase #3	$154.99	9.470%	$169.6676	$169.67	$169.65	$169.70
Purchase #4	$89.99	11.520%	$100.3568	$100.36	$100.35	$100.40
Purchase #5	$78.98	12.807%	$89.095	$89.10	$89.10	$89.10
Purchase #6	$74.29	12.678%	$83.7085	$83.71	$83.70	$83.70
Purchase #7	$229.86	3.753%	$238.4866	$238.49	$238.50	$238.50
7 purchase totals =	$962.43		$1,032.1180	$1,032.13	$1,032.10	$1,032.20