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	$39.88	13.652%	$45.3244	$45.32	$45.30	$45.30
Purchase #2	$175.51	9.174%	$191.6113	$191.61	$191.60	$191.60
Purchase #3	$198.64	3.441%	$205.4752	$205.48	$205.50	$205.50
Purchase #4	$110.48	8.382%	$119.7404	$119.74	$119.75	$119.70
Purchase #5	$228.88	6.474%	$243.6977	$243.70	$243.70	$243.70
Purchase #6	$130.69	12.331%	$146.8054	$146.81	$146.80	$146.80
Purchase #7	$55.92	9.752%	$61.3733	$61.37	$61.35	$61.40
7 purchase totals =	$940.00		$1,014.0277	$1,014.03	$1,014.00	$1,014.00