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	$108.54	10.482%	$119.9172	$119.92	$119.90	$119.90
Purchase #2	$165.76	8.354%	$179.6076	$179.61	$179.60	$179.60
Purchase #3	$170.48	11.629%	$190.3051	$190.31	$190.30	$190.30
Purchase #4	$97.83	8.849%	$106.487	$106.49	$106.50	$106.50
Purchase #5	$104.85	11.347%	$116.7473	$116.75	$116.75	$116.70
Purchase #6	$126.33	4.786%	$132.3762	$132.38	$132.40	$132.40
Purchase #7	$100.93	3.796%	$104.7613	$104.76	$104.75	$104.80
7 purchase totals =	$874.72		$950.2017	$950.22	$950.20	$950.20