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	$31.94	10.736%	$35.3691	$35.37	$35.35	$35.40
Purchase #2	$230.86	9.670%	$253.1842	$253.18	$253.20	$253.20
Purchase #3	$56.69	11.163%	$63.0183	$63.02	$63.00	$63.00
Purchase #4	$98.51	12.757%	$111.0769	$111.08	$111.10	$111.10
Purchase #5	$88.53	3.712%	$91.8162	$91.82	$91.80	$91.80
Purchase #6	$164.80	13.330%	$186.7678	$186.77	$186.75	$186.80
Purchase #7	$53.28	11.429%	$59.3694	$59.37	$59.35	$59.40
7 purchase totals =	$724.61		$800.6019	$800.61	$800.55	$800.70