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	$191.36	4.514%	$199.998	$200.00	$200.00	$200.00
Purchase #2	$103.93	12.469%	$116.889	$116.89	$116.90	$116.90
Purchase #3	$174.37	5.108%	$183.2768	$183.28	$183.30	$183.30
Purchase #4	$154.47	7.147%	$165.51	$165.51	$165.50	$165.50
Purchase #5	$19.67	11.254%	$21.8837	$21.88	$21.90	$21.90
Purchase #6	$187.80	5.550%	$198.2229	$198.22	$198.20	$198.20
Purchase #7	$89.63	6.587%	$95.5339	$95.53	$95.55	$95.50
7 purchase totals =	$921.23		$981.3143	$981.31	$981.35	$981.30