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	$173.46	7.871%	$187.113	$187.11	$187.10	$187.10
Purchase #2	$171.61	8.804%	$186.7185	$186.72	$186.70	$186.70
Purchase #3	$174.43	9.470%	$190.9485	$190.95	$190.95	$190.90
Purchase #4	$189.47	13.669%	$215.3687	$215.37	$215.35	$215.40
Purchase #5	$205.90	8.466%	$223.3315	$223.33	$223.35	$223.30
Purchase #6	$133.75	13.362%	$151.6217	$151.62	$151.60	$151.60
Purchase #7	$58.86	3.651%	$61.009	$61.01	$61.00	$61.00
7 purchase totals =	$1,107.48		$1,216.1109	$1,216.11	$1,216.05	$1,216.00