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	$89.88	7.639%	$96.7459	$96.75	$96.75	$96.70
Purchase #2	$130.27	9.466%	$142.6014	$142.60	$142.60	$142.60
Purchase #3	$202.32	3.570%	$209.5428	$209.54	$209.55	$209.50
Purchase #4	$104.62	11.448%	$116.5969	$116.60	$116.60	$116.60
Purchase #5	$12.65	5.698%	$13.3708	$13.37	$13.35	$13.40
Purchase #6	$41.80	9.863%	$45.9227	$45.92	$45.90	$45.90
Purchase #7	$186.59	7.230%	$200.0805	$200.08	$200.10	$200.10
7 purchase totals =	$768.13		$824.8610	$824.86	$824.85	$824.80