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	$42.32	7.571%	$45.524	$45.52	$45.50	$45.50
Purchase #2	$107.99	11.389%	$120.289	$120.29	$120.30	$120.30
Purchase #3	$50.62	5.115%	$53.2092	$53.21	$53.20	$53.20
Purchase #4	$95.85	8.504%	$104.0011	$104.00	$104.00	$104.00
Purchase #5	$90.38	13.739%	$102.7973	$102.80	$102.80	$102.80
Purchase #6	$38.57	9.578%	$42.2642	$42.26	$42.25	$42.30
Purchase #7	$141.60	7.359%	$152.0203	$152.02	$152.00	$152.00
7 purchase totals =	$567.33		$620.1051	$620.10	$620.05	$620.10