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	$203.57	10.506%	$224.9571	$224.96	$224.95	$225.00
Purchase #2	$160.55	7.423%	$172.4676	$172.47	$172.45	$172.50
Purchase #3	$181.89	4.448%	$189.9805	$189.98	$190.00	$190.00
Purchase #4	$171.61	11.394%	$191.1632	$191.16	$191.15	$191.20
Purchase #5	$169.83	12.783%	$191.5394	$191.54	$191.55	$191.50
Purchase #6	$58.55	7.200%	$62.7656	$62.77	$62.75	$62.80
Purchase #7	$169.67	5.471%	$178.9526	$178.95	$178.95	$179.00
7 purchase totals =	$1,115.67		$1,211.8260	$1,211.83	$1,211.80	$1,212.00