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	$100.95	13.278%	$114.3541	$114.35	$114.35	$114.40
Purchase #2	$217.80	11.619%	$243.1062	$243.11	$243.10	$243.10
Purchase #3	$170.96	7.848%	$184.3769	$184.38	$184.40	$184.40
Purchase #4	$118.76	10.589%	$131.3355	$131.34	$131.35	$131.30
Purchase #5	$89.58	10.768%	$99.226	$99.23	$99.25	$99.20
Purchase #6	$182.86	9.372%	$199.9976	$200.00	$200.00	$200.00
Purchase #7	$106.53	9.424%	$116.5694	$116.57	$116.55	$116.60
7 purchase totals =	$987.44		$1,088.9657	$1,088.98	$1,089.00	$1,089.00