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	$211.67	12.447%	$238.0166	$238.02	$238.00	$238.00
Purchase #2	$82.48	8.493%	$89.485	$89.49	$89.50	$89.50
Purchase #3	$6.69	5.183%	$7.0367	$7.04	$7.05	$7.00
Purchase #4	$168.81	12.746%	$190.3265	$190.33	$190.35	$190.30
Purchase #5	$42.82	7.824%	$46.1702	$46.17	$46.15	$46.20
Purchase #6	$110.78	6.741%	$118.2477	$118.25	$118.25	$118.20
Purchase #7	$55.79	3.769%	$57.8927	$57.89	$57.90	$57.90
7 purchase totals =	$679.04		$747.1754	$747.19	$747.20	$747.10