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	$174.72	13.313%	$197.9805	$197.98	$198.00	$198.00
Purchase #2	$6.65	12.288%	$7.4672	$7.47	$7.45	$7.50
Purchase #3	$176.59	9.160%	$192.7656	$192.77	$192.75	$192.80
Purchase #4	$38.38	10.772%	$42.5143	$42.51	$42.50	$42.50
Purchase #5	$12.38	9.316%	$13.5333	$13.53	$13.55	$13.50
Purchase #6	$41.36	10.340%	$45.6366	$45.64	$45.65	$45.60
Purchase #7	$92.66	13.835%	$105.4795	$105.48	$105.50	$105.50
7 purchase totals =	$542.74		$605.3770	$605.38	$605.40	$605.40