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	$109.28	6.692%	$116.593	$116.59	$116.60	$116.60
Purchase #2	$174.53	9.393%	$190.9236	$190.92	$190.90	$190.90
Purchase #3	$185.37	4.292%	$193.3261	$193.33	$193.35	$193.30
Purchase #4	$98.41	3.661%	$102.0128	$102.01	$102.00	$102.00
Purchase #5	$216.83	5.260%	$228.2353	$228.24	$228.25	$228.20
Purchase #6	$230.43	8.445%	$249.8898	$249.89	$249.90	$249.90
Purchase #7	$178.43	6.833%	$190.6221	$190.62	$190.60	$190.60
7 purchase totals =	$1,193.28		$1,271.6027	$1,271.60	$1,271.60	$1,271.50