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	$196.65	13.728%	$223.6461	$223.65	$223.65	$223.60
Purchase #2	$222.87	6.788%	$237.9984	$238.00	$238.00	$238.00
Purchase #3	$111.38	3.264%	$115.0154	$115.02	$115.00	$115.00
Purchase #4	$47.84	7.867%	$51.6036	$51.60	$51.60	$51.60
Purchase #5	$101.71	9.393%	$111.2636	$111.26	$111.25	$111.30
Purchase #6	$91.71	7.838%	$98.8982	$98.90	$98.90	$98.90
Purchase #7	$140.41	10.277%	$154.8399	$154.84	$154.85	$154.80
7 purchase totals =	$912.57		$993.2652	$993.27	$993.25	$993.20