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	$188.70	6.239%	$200.473	$200.47	$200.45	$200.50
Purchase #2	$69.38	5.746%	$73.3666	$73.37	$73.35	$73.40
Purchase #3	$56.69	4.632%	$59.3159	$59.32	$59.30	$59.30
Purchase #4	$100.73	9.263%	$110.0606	$110.06	$110.05	$110.10
Purchase #5	$25.58	7.700%	$27.5497	$27.55	$27.55	$27.50
Purchase #6	$161.62	8.161%	$174.8098	$174.81	$174.80	$174.80
Purchase #7	$102.96	11.199%	$114.4905	$114.49	$114.50	$114.50
7 purchase totals =	$705.66		$760.0661	$760.07	$760.00	$760.10