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	$192.30	7.144%	$206.0379	$206.04	$206.05	$206.00
Purchase #2	$5.79	13.853%	$6.5921	$6.59	$6.60	$6.60
Purchase #3	$148.67	12.487%	$167.2344	$167.23	$167.25	$167.20
Purchase #4	$42.25	12.342%	$47.4645	$47.46	$47.45	$47.50
Purchase #5	$27.41	11.595%	$30.5882	$30.59	$30.60	$30.60
Purchase #6	$88.66	9.344%	$96.9444	$96.94	$96.95	$96.90
Purchase #7	$81.96	9.149%	$89.4585	$89.46	$89.45	$89.50
7 purchase totals =	$587.04		$644.3200	$644.31	$644.35	$644.30