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	$40.92	10.493%	$45.2137	$45.21	$45.20	$45.20
Purchase #2	$105.52	4.812%	$110.5976	$110.60	$110.60	$110.60
Purchase #3	$85.53	5.506%	$90.2393	$90.24	$90.25	$90.20
Purchase #4	$152.71	8.629%	$165.8873	$165.89	$165.90	$165.90
Purchase #5	$29.41	5.624%	$31.064	$31.06	$31.05	$31.10
Purchase #6	$225.33	5.838%	$238.4848	$238.48	$238.50	$238.50
Purchase #7	$102.50	11.821%	$114.6165	$114.62	$114.60	$114.60
7 purchase totals =	$741.92		$796.1032	$796.10	$796.10	$796.10