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	$231.93	3.242%	$239.4492	$239.45	$239.45	$239.40
Purchase #2	$52.48	13.492%	$59.5606	$59.56	$59.55	$59.60
Purchase #3	$239.64	6.545%	$255.3244	$255.32	$255.30	$255.30
Purchase #4	$237.78	3.191%	$245.3676	$245.37	$245.35	$245.40
Purchase #5	$84.69	6.206%	$89.9459	$89.95	$89.95	$89.90
Purchase #6	$225.97	4.190%	$235.4381	$235.44	$235.45	$235.40
Purchase #7	$83.62	9.207%	$91.3189	$91.32	$91.30	$91.30
7 purchase totals =	$1,156.11		$1,216.4047	$1,216.41	$1,216.35	$1,216.30