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	$187.49	10.435%	$207.0546	$207.05	$207.05	$207.10
Purchase #2	$95.60	3.142%	$98.6038	$98.60	$98.60	$98.60
Purchase #3	$86.96	9.244%	$94.9986	$95.00	$95.00	$95.00
Purchase #4	$250.96	9.272%	$274.229	$274.23	$274.25	$274.20
Purchase #5	$155.94	7.389%	$167.4624	$167.46	$167.45	$167.50
Purchase #6	$227.38	10.192%	$250.5546	$250.55	$250.55	$250.60
Purchase #7	$160.71	11.309%	$178.8847	$178.88	$178.90	$178.90
7 purchase totals =	$1,165.04		$1,271.7877	$1,271.77	$1,271.80	$1,271.90