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	$205.57	13.820%	$233.9798	$233.98	$234.00	$234.00
Purchase #2	$65.70	9.757%	$72.1103	$72.11	$72.10	$72.10
Purchase #3	$248.34	3.227%	$256.3539	$256.35	$256.35	$256.40
Purchase #4	$17.62	10.627%	$19.4925	$19.49	$19.50	$19.50
Purchase #5	$227.43	9.283%	$248.5423	$248.54	$248.55	$248.50
Purchase #6	$129.64	8.197%	$140.2666	$140.27	$140.25	$140.30
Purchase #7	$29.66	5.500%	$31.2913	$31.29	$31.30	$31.30
7 purchase totals =	$923.96		$1,002.0367	$1,002.03	$1,002.05	$1,002.10