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	$196.88	9.321%	$215.2312	$215.23	$215.25	$215.20
Purchase #2	$248.55	3.510%	$257.2741	$257.27	$257.25	$257.30
Purchase #3	$184.54	6.417%	$196.3819	$196.38	$196.40	$196.40
Purchase #4	$38.71	8.278%	$41.9144	$41.91	$41.90	$41.90
Purchase #5	$198.62	5.198%	$208.9443	$208.94	$208.95	$208.90
Purchase #6	$203.32	6.592%	$216.7229	$216.72	$216.70	$216.70
Purchase #7	$19.67	4.722%	$20.5988	$20.60	$20.60	$20.60
7 purchase totals =	$1,090.29		$1,157.0676	$1,157.05	$1,157.05	$1,157.00