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	$85.78	10.534%	$94.8161	$94.82	$94.80	$94.80
Purchase #2	$199.43	4.305%	$208.0155	$208.02	$208.00	$208.00
Purchase #3	$119.52	5.304%	$125.8593	$125.86	$125.85	$125.90
Purchase #4	$155.43	9.697%	$170.502	$170.50	$170.50	$170.50
Purchase #5	$184.85	6.478%	$196.8246	$196.82	$196.80	$196.80
Purchase #6	$215.98	11.137%	$240.0337	$240.03	$240.05	$240.00
Purchase #7	$103.69	12.226%	$116.3671	$116.37	$116.35	$116.40
7 purchase totals =	$1,064.68		$1,152.4183	$1,152.42	$1,152.35	$1,152.40