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	$211.50	5.754%	$223.6697	$223.67	$223.65	$223.70
Purchase #2	$172.88	9.627%	$189.5232	$189.52	$189.50	$189.50
Purchase #3	$185.28	12.453%	$208.3529	$208.35	$208.35	$208.40
Purchase #4	$213.82	3.854%	$222.0606	$222.06	$222.05	$222.10
Purchase #5	$223.90	9.551%	$245.2847	$245.28	$245.30	$245.30
Purchase #6	$238.79	4.757%	$250.1492	$250.15	$250.15	$250.10
Purchase #7	$86.27	10.740%	$95.5354	$95.54	$95.55	$95.50
7 purchase totals =	$1,332.44		$1,434.5757	$1,434.57	$1,434.55	$1,434.60