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	$166.88	13.552%	$189.4956	$189.50	$189.50	$189.50
Purchase #2	$189.79	3.772%	$196.9489	$196.95	$196.95	$196.90
Purchase #3	$62.85	10.419%	$69.3983	$69.40	$69.40	$69.40
Purchase #4	$148.37	5.322%	$156.2663	$156.27	$156.25	$156.30
Purchase #5	$224.97	10.542%	$248.6863	$248.69	$248.70	$248.70
Purchase #6	$39.38	3.284%	$40.6732	$40.67	$40.65	$40.70
Purchase #7	$104.77	9.824%	$115.0626	$115.06	$115.05	$115.10
7 purchase totals =	$937.01		$1,016.5312	$1,016.54	$1,016.50	$1,016.60