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	$95.73	3.393%	$98.9781	$98.98	$99.00	$99.00
Purchase #2	$171.47	7.152%	$183.7335	$183.73	$183.75	$183.70
Purchase #3	$12.60	5.300%	$13.2678	$13.27	$13.25	$13.30
Purchase #4	$150.45	9.350%	$164.5171	$164.52	$164.50	$164.50
Purchase #5	$217.33	3.171%	$224.2215	$224.22	$224.20	$224.20
Purchase #6	$63.96	6.177%	$67.9108	$67.91	$67.90	$67.90
Purchase #7	$154.83	4.559%	$161.8887	$161.89	$161.90	$161.90
7 purchase totals =	$866.37		$914.5175	$914.52	$914.50	$914.50