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	$111.67	4.755%	$116.9799	$116.98	$117.00	$117.00
Purchase #2	$170.59	6.260%	$181.2689	$181.27	$181.25	$181.30
Purchase #3	$125.62	13.421%	$142.4795	$142.48	$142.50	$142.50
Purchase #4	$147.99	4.597%	$154.7931	$154.79	$154.80	$154.80
Purchase #5	$74.32	4.114%	$77.3775	$77.38	$77.40	$77.40
Purchase #6	$211.61	5.788%	$223.858	$223.86	$223.85	$223.90
Purchase #7	$197.94	12.540%	$222.7617	$222.76	$222.75	$222.80
7 purchase totals =	$1,039.74		$1,119.5186	$1,119.52	$1,119.55	$1,119.70